I once had alt-enter screw up the full-screen toggle option real nicely... the game thought it was set the other way (e.g. in window when it was really full screen and vice versa).

Another bug: when I press ALT (e.g. for ALT+TAB to switch to another window) and, then, after some time passes, ENTER (e.g. to answer a question), the game goes full screen.

Maybe the devs want you to always devote your time to IVAN when the window is up, and if you try to divert away to something else, it crashes because it's angry at you! I ALWAYS have my game in windowed mode, because if I ever put it in fullscreen it plays like I have my color settings on 16 bit (everything turns a nasty yellow and weird greens)

It runs too quickly for me if I run it full-screen. I often use the "go" command to get somewhere and then stop it in mid "go" (BTW side note: the go command is currently not very smart. Would be useful if it would stop at doors at least.), but if the game is full-screen I can't do that because my character moves so quickly...

We are aware of some problems which arise when pressing ALT+something. Alas, we really don't have energy to do the necessary research to correct these platform-specific issues. They aren't really fatal, and we probably do more good by allocating the time to adding new features or fixing bugs in the gameplay itself. If someone with programming experience has had similiar problems and knows how to fix them, you could look at FeLib/Source/whandler.cpp where the window and key handling codes are and check if he could contribute a patch. It shouldn't be too difficult actually, as we have received a patch or two to this file previously, too.