Try reinstalling the game?

Er yeah, I've done that, twice. I've tried on different drives - and it works fine on the other computers in the house, just not mine. >.<

I even tried installing the old Quicktime 3 from my game CD's as a last resort.

You could try doing a System Restore and restoring back to a date before you did the graphics card update. My guess is that something in the update changed the registry or mouse settings and it wasn't corrected when you rolled back to the earlier version. You could also try updating your mouse drivers or rolling them back to an earlier version, if it looks like that was updated recently, too.

System restore didn't work. Uninstalled graphics card drivers, updated to newest. Uninstalled Logitech mouse driver and reinstalled (I recently got a new mouse, but it's the same mouse model). It's still crashing on left-mouse-click (If I restore a game, I can change between look and interact fine, but the moment I try to left-click, it crashes)

I've checked with the GOG version of Mask of Eternity, and no crash-on-click issues there.

I'm at the point of thinking it's a really stupid, really easy fix and I'm overcomplicating it.

Is your old mouse dead or can you try plugging that one in to see if your new mouse might be defective? Or, if you have a basic mouse, with just left & right buttons and a scroll wheel, lying around try that in the game. If either of those does the trick, then it's probably a mouse issue.

I do know Logitech has a section for game settings in their Setpoint software. So, try updating those settings. If you are just using the Windows drivers, then try installing the latest Setpoint software for your mouse and see if that helps.

BTW, when you said System Restore didn't work, did it finish but the results are the same? Or did it fail to restore?

Using a Logitech G700 - and I did try the old mouse out of curiosity, and it still crashes.

Never thought of tinkering with the setpoint, maybe something in that's causing a conflict. Will have to tinker.

And the system restore failed - one of the problems I've had with Vista :-/ I even tried running the game with Avast turned off (it has a habit of blocking games in a sandbox mode). I'll try to mess with settings in Setpoint and see if that fixes it, but other than that, I'm still at a loss.

What are your compatibility mode settings?

Compatabilities dont' change a thing, I've tried running with every setting there - sometimes I even get a "DirectX 5.0 not installed" error. Go figure, yet if I try to install it from my CD's, it says it's already installed (which I already knew)

Setpoint’s not compatible with the G700, so I uninstalled it in hopes it was causing issues with the Logitech Gaming Software. No dice. I’ve run Advanced System Care, Glary Utilities, Avast, Spybot, anything I could think of, and nothing’s working.

Now, the really confusing part is this - even though the GOG version ran fine 2 months ago, my CD install of QFG5 from my old discs still runs fine – doesn’t crash on me when I try to play it. Neither does the old install on my external drive – no crashing and runs perfectly fine.

This really REALLY has me confused now – I started installing all my classic DOS games to the same drive and folder to keep things organized for me, and out of all of them, QFG5’s the only one that’s not working, and it’s from the latest GOG installer.

It's either a bad DL like you said, or a massive conflict between my system and that installer. I uninstalled and installed from the old original download I remembered I had on my one flash drive, and everything works fine.

I just re-downloaded the 2.0.0.32 installer again - and after uninstalling the older 1.0 install - same issue as before, crash on left-click. Think I'm just going to not fuss with it until GOG releases another minor update - maybe it's just not liking my computer. Either way, at least I've got it working now, and can play past the Minos and Dragon crashes.

As for it not running right on C: I'd try it (Most my games are on F: ) but I've never had any issue with QFG5 playing on any non-C: before. (I usually keep my C: partitioned and used for 'important' programs and install everything else on other partitions)

Well, at least you got to the bottom of it and it's working now. Have fun slaying the dragon!