I sucessfully upgraded to 4 today…but this evening had difficulty downloading paintstop and uv master to zbrush.Now when I try to open zbrush I get the icon on my bottom taskbar with the bell sound but no zbrush. Ive tried from the start menu and shortcut with no results.
Same problem here.
However when you double click on the icon in the taskbar ZBrush wil then open on your screen.
It is rather strange.
It happend after I uninstalled ZBrush 3.5??
It seems theirs compatibility issues while running Win 7 for me anyhow.I just cant launch zbrush correctly. 
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Just installed v4 this morning - same problem as OP; the icon just sits on the taskbar and nothing happens. I found that if I run as Administrator it seems to work OK… so far, although it isn’treally ideal.
I had the same problem, although mine wouldn"t open up if I double clicked the icon. I went into the startup folder and deleted all of the plugins and now everything works fine. I hope it will be fixed soon so we can utilize those applications.
Ive deleted everything to no avail.
Digging around on clean installs I found out that you have to go to your C drive for any remaining folders in which I did find some remaining.So with a new install for the 3rd time it worked.No more compatibility issues.So I think now that I should wait to download the 2 new plugins for Z4 until the bugs if any are out.Thats where all my problems started in the first place.Hopes this helps anyone with similiar probs.
Same irritating problem, except for me, everything was working fine (plugins and all) but ZB4 just decided not to open up one day. Like others have said, it just hangs in the tool bar. If I hover the mouse over the ZB4 icon in the tool bar a small (teaser) image of the supposedly active ZB4 window appears, but the real deal is inaccessible. I’ve tried running the program under administration and as a normal user to no avail.
Aurick?
Mine is working now.Make sure that their is no plugins or other files in your startup file.
When customizing the ZBrush folder, make sure to not copy any ZBrush files (such as plugins) from and older ZBrush version. This will likely result in hard to track problems.
Try the following steps…
[COLOR=White]1. Delete the following files (if exists)…
ZStartup
ConfigFilesZBrushWindowStartupSize.cfg
ZStartupTempFiles folderimages.mem
ZStartupTempFiles foldersearch.mem
ZStartupTempFiles folderthumbnails.mem
- If you have a ZStartup
CustomUserInterface35.cfg file, then rename it to oldCustomUserInterface35.cfg
Launch ZBrush. If you still encounter the problem then exit ZBrush and try step 3.
- Double-click the ZBrush icon and immediately press and hold the SHIFT key. This will launch ZBrush and temporarily disable all user plugins.
If step 3 resolved the problem, then you have a plugin related problem.
If all fails, then I recommend that you re-install ZBrush. If you then need to customize ZBrush by adding plugins, add one at a time and only if successful, continue with the next plugin.
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I just went ahead and reinstalled it and its working fine now. Point is I shouldn’t have to do this, a real headache.
Thank you for your suggestion.
Thanks Support, we were typing at the same time. I’ll keep your solution on hand just in case zb4 acts up again. Since I don’t know what caused it to stop working, its likely I’ll need to use your suggestion in the future.
I’m suddenly having the same problem. I had no problems with the initial install and have been working along merrily since the day i installed it. Everything was working fine last night. This morning I double clicked on the short cut got that “bell” tone and nothing opened onto my screen. I tried rebooting…nothing seems to be working. 
You may just have to reinstall the program. Mine has been running fine since I did this, but I have no idea if or when I might have to do it again.
Make sure to back up any tools or projects you have saved.
That was a wierd one. I did reinstall and all seems well now, but what a waste of a Sunday afternoon… . Now I need to go and put everything back in place. ek.