Glad it works for you now. I have always had my permissions set up the way you described. It only work for me when Sav pointed out changing the Zbrush folder name to “ZBrush2”. The problem seems to be both permissions and path names.
I think we’ll have a solution for the other users having problems real soon.
Thanks for sharing your information.
Additional info: My ZBrush is installed on a hard dive that is formatted for OS 9. Just to keep everything grouped together, I have all my OS 9 and OS X art programs on this drive.
I haven’t tracked it down yet, but for some reason when I run the newly installed ZBrush from the root window (the one that opens when you double-click on the hard drive) ZApplink works fine. But when I drag it into my OS 9 application folder>Art folder (where it used to be) ZBrush works, but ZAppLink wont work. So before going to all the trouble changing Owner & Permissions, try moving it to a different location on your drive (such as the root folder) to see if it makes a difference.
I think cy is correct. It may also be a path problem.
At the root level make a path like this
APPLICATIONS/ZBrush2/ZBrush2.app
For me it works everytime no more errors.
make sure ZBrush2.app is named correctly(Use Get info dialog to change name) and make applications all caps just to be safe.
Well i renamed my zbrush app to Zbrush2… no spaces… and now i make it to photoshop… but im at the same place where Zbrush crashes when i attempt to pick up the object again. 
tried the all CAPS APPLICATIONS folder… and played with some permissions, even on teh apps folder… no dice… _Ken
how I got it to work on my mac
Install Zbrush on the user level not the Admin level
change folder containing app name to “ZBrush2”
Set all permissions to read & write
named the application ZBrush2.app
set Owner to Master Admin Name
set Group to User
Works perfectly
ok, i followed Cy’s instructions, and it still did not work 
I did not re-install Zbrush on a different user level BTW.
So how did i get it to work. I played more with permissions.
I set my permissions on the Zdata folder, Zstartup folder and certianlty all the Zapplink data , Zplugs… etc to Read & write for everything, apply to all enclosed, for anything i though ZB and Photoshop would be access, and a clear permissions path into the zbrush and zapplink folder.
Now i just need to edit the path so it goes to CS2 instead of CS now. I also have my APPLICATIONS folder all caps, Zbrush2.app on the application, and no space on the Zbrush2 folder.
Obvioulsy the issue was that the “external image editor” was unable to write/give the new data back to zbrush.
Again it would be cool if Pixo added a button to the Zapplink interface so that u could pic a different image editor if u needed tools from various apps, or if apps get moved, or upgraded. Thanks Cy, hope this helps a lot of ppl -Ken
*** ok, i got ahead of myself… its still not fixed… im gonna switch back to CS and see if ZB no longer crashes on pickup from projection master… i did get it to launch CS2, and to “accept changes” and dynamically update the change i made in photoshop… But ZB crashed when i tried to pickup from PM so i could rotate my model :(. I also however make ZB crash when i imported a photo to PS and then merged layers, since the image comes in a on a different layer… most success has just been painting on the defualt layer your on in PS when ZB launches your external editor.
ok, ive been playing with CS and CS2, same result. Thought that maybe cuz CS was the app i selected on the maidan run of teh script there was some miss matched data… nope…
ok, so ive gotten Zbrush to “accept changes” again. BUT the connection bewteen ZB - specifically projection master, and Photoshop is still weak. I only get the ZB to update my changes if i switch back to ZB, and click the “return to external editor” button… then Zbrush wakes up and sees there a difference, and askes if i’d like to accept changes… i do, and voila… my new texture is there on my geom… BUT… just by pressing the “g” key… and openning Projection master to pick up the model and spin is a Crash everytime. Theres obviously an issue where ZB, or PM cant get the photoshop changes, some sorta mismatch.
BTW i noticed that the PSD that Zbrush makes to ship to photoshop (or whatever your psd editor of choice is) has these permissions everytime… they get over written when i change them the next time i link. And becomes read only everytime Zbrush writes to that file, ie. when its updated.
BTW, i have been able to get images to work, deleted the “background” layer, renamed etc succesffully. The problem is the same in CS, or CS2, projection master crashes with the new texture applied to your model. I assume the reason i see the new texture file is being update the texture is being updated (duh), PM just cant project this new data onto the 3d object. Assuming there isnt some data mismatch somewhere PM is looking for and cant find, but had.
I tried all this stuff without success.
There seems an oddity with renaming the ZBrush app file though. I rename it in the get info box and it stays as ZBrush2.app, but in the finder it is still just ‘ZBrush2’. Would that be significant?
Sav
[QUOTE=spaz8]ok, i followed Cy’s instructions, and it still did not work I did not re-install Zbrush on a different user level BTW.
You did not follow all my instructions:evil:
That may be why it is not working.
Install Zbrush at the user level see if that works. It worked for me and my setup looks similar to yours.
If that does not work. I will send you some more info on my system setup I think we are near narrowing down the problem.
No I do not think it matters. Does the same thing on mine and Zapp is working. I am Zappping all over place. 
I am also encountering ZappLink errors. After following the thread. (Mainly the space removal in the Zbrush folder.) I was able to get Photoshop to launch and open my image. After edits are saved in PSD, Zbrush crashes as soon as I return.
My apps are not on my root volume (ie NOT the applications folder Apple stores all of its apps in) but on another volume with the user folder. I can’t move Zbrush because it would require reauthorization. Is this the same setup that’s causing everyone else grief?
DP G4 1GHZ, 1.75 GB, 10.3.9, ATI 9800 2x20" Zbrush 2.02
The error message is still apperent as I posted earlier in this thread.
even after trying all the suggestions - no change for me.
it just gets a little bit confusing with all the posibilities and options that you guys offer.
However, I decided to keep away from trying to use ZApp until a solution appears from the pixologic team. In the mean time I like to do other things. There is also a life out there.
ciao voolger
Gatz you may want to upgrade from Z2.02 to version 2.03.
See if that helps.
Where is the patch/upgrade to 2.03? I haven’t found any reference to it anywhere.
THX
Thanks Cy!
I was having the same problem as Gatz. Upgrading to 2.03 made all the difference.
Gatz, did you find the updater? If not, here’s the link to where I found it.
Email pixologic and ask for the link to the installer.
Yes! The 2.03 patch worked.
So the short version of the fix–for the lazy sods that skip to the latest post;): eliminate spaces in your folder name, make sure permissions allow read and write for all items in your zbrush folder and make sure you have the latest ZB (2.03)
This is what fixed it for me. My Zbrush and PhotoShop are NOT in my root drive apps folder.
Thanks all!!
DP G4 1GHZ, 1.75 GB, 10.3.9, ATI 9800 2x20" ZBrush 2.03
i’m afraid my issues with Zapplink arent gonna be resolved… i have no spaces as far as im aware from my volume name all the way to the app. I’ve been running 2.03 since about the same hour it was released a year ago. And all my permissions on just everything i can think of in the zbrush folder and its contents have and been made read/write etc.
Hoping Rev 3 is in the works still…
For anyone else who might not have updated to 2.03, you can find the updaters here.
If anyone has updated to 2.03, has no spaces in any folder or path names, and is still having trouble with ZAppLink, please send a detailed email to [email protected]. Be sure to include the exact nature of the problem that you’re having, your operating system version number, the program you’re trying to use ZAppLink with, and as much system information as you can think of.
Gatz and Mcarrel glad U got it to work.
Spaz install Zbrush at the user level not at the
Admin level. Update to 2.03
Launch Zbrush from the user level.
Try that and see if it works.