Yeah I figured the ALT-TAB thing was to be expected. Not a big deal. Photoshop often doesn’t detect Wacom pressure-sensitivity if you ALT-TAB or start a new application while it’s booting, too.
Regarding my system, something that may or may not make a difference is that I do not have a C:\ drive defined - Windows is installed on my primary drive F:</b> (250gb SATA drive with 193gb free space), this is also where ZBrush resides. I have a second 250gb SATA drive, G:, but that doesn’t store any ZBrush or system data. I doubt free space is the issue 
I haven’t defragged in a few months though, I’ll give that a shot tonight.
I run Grisoft’s AVG Free as my virus scanner, it does a pass every day and my system appears to be clean. Same report from HijackThis. I haven’t received any notifications or warnings when running ZBrush.
As far as I know, all of my CompactMem, Undo and MaxPolysPerMesh settings are the default. I certainly haven’t manually changed any of them, I’ll list them here just in case though:
Compact Mem: 256
Doc Undo: 4
Tool Undo: 4
MaxPolyPerMesh: 6
HD Preview MaxPoly: 4
When it runs, it usually runs fine for hours without a hitch. It’s just the getting it past the initialisation that’s the hard part 
Further info which may be of use: I have a StartupDocument.ZBR saved in
the ZStartup folder, but removing it doesn’t affect the startup crashes. Similarly I have a ZPlug (gm770’s Make1Mesh plugin), but removing it or adding it from the ZPlugs folder doesn’t appear to have any effect on crashes either.
Also, I run a dual monitor setup, primary is widescreen LCD at 1680x1050 which I run ZBrush on, secondary is a 4:3 flat panel 1280x1024. I have my Wacom Intuos2 set up to use only the primary monitor while ZBrush is running (set up through the Wacom options). The rest of the time it’s mapped over both monitors. I guess I should try not using the tablet and uninstalling the drivers for a while to see if it makes any difference.
Question: Is there a setting to turn off the “Quick Load” screen that pops up on startup with the 5-6 last used ZTL files listed as preview icons? I’m sure there was a setting for that in ZB3 but I can’t seem to find it in 3.1 … maybe that’d make a difference too.
Thanks for the support so far!
Edit: Heh, I had ZBrush 3.1 open while I was typing this, to check the settings… I had a ZTL open, and then switched to a Sphere3D default tool, and tried to sculpt on it without converting it to a PolyMesh3D - I got the popup warning about “Make PolyMesh3D”, and at the same instant it crashed… but after I’d ended the task, this time when I tried re-launching it, ZBrush ran again perfectly, straight away! Weird 