It sounds like a problem with DirectX switching back to the desktop resolution. Does it work if you right click on an open area of the desktop to get into the Display Settings, change the resolution, apply and switch it back?
A program like
DesktopOK would let you save and restore desktop icon positions, in case lowering the resolution moves anything.
Did you cut the resolution in half? If that quarter of the screen corresponds to what the game was at, there may still be something strange going on with how the game is exiting.
Try the
4GB Patch to increase the amount of virtual memory that the game (or any 32 bit application) can access in 64 bit versions of Windows. It has helped with some startup crashes and graphics issues in the older Divinity games, and a threading issue in Divinity 2, so it couldn't hurt to try.
