i think i found the reason for my crashes
yesterday i decided to give it another shot. i updated all drivers i could find, also several mainboard drivers (such as sata or network driver), i even updated the bios. The game still crashed.
i decided to install it on my laptop, plugged the laptop into my TV, hooked up my arcade stick and started playing: crash at school.
more or less out of desparation i gave it another shot on my desktop system, without the arcade stick, and the game didn't crash. i played through the whole prologue and a bit further, it took me 2 to 3 hours and i didn't have a crash, where as usually i'd crash even before i could finish exploring the school.
so just now i made a few more tests. result: if i plug in my arcade stick, whether XPadder is running or not, whether i use the stick or not the game crashes. ok, when not using xpadder and not using the arcade stick (which doesn't work without xpadder anyway, but more about that later), the game crashed only when i wante to close it (by choosing Exit from the games main menu) after about 5 minutes running around school.
the arcade stick i'm using is a Hori Real Arcade Pro EX-SE, or HRAP EX-SE in short, see here http://www.amazon.com/Xbox-360-Real-Arcade-Pro-EX-SE/dp/B002FKYPU4
. i modded it by replacing the front plate and some buttons, but that shouldn't make a differnce. it's an xbox controller and windows recognizes it as such. but the game doesn't react to the stick at all, not even in the gamepad configuration. the controller works in windows setup.
i also have a joystick hooked up (Logitech Freedom 2.4), which the game DOES recognize as controller. i also tried to unplug it, and now the menu option to configure game controllers in the Fortune Summoners menu is disabled. I tried it once more with an unplugged joystick (maybe FS doesn't like multiple game controllers) and with XPadder (otherwise i can't use the stick), the game crashed again when properly closing it after a few minutes running around school.
So my cause for the crash seems to be the HRAP EX-SE. The cause for the crash might be connected to the reason why the game doesn't recognize it as a controller, even though it's an XBox controller (and works without problems on the XBox and in Windows itself)
If you need any more information about the stick or the drivers let me know what you need/want.