The game worked fine before numerous times but when I went back to play today the game won't open and gives me the message I wrote in the title.

I'm using Vista Home Edition.

If there is a easy solution to this, please let me know. Thanks.

There's a couple of things you could try out.
1. Have you tried to run the executable inside the Sanitarium folder instead of the default GOG
wrapped one?
If not, try to run it, if it works make a new save and try to run the default GOG wrapped executable again.

2. Is the game installed outside the default "Program Files" folder?
If not, install the game outside this folder (e.g. C:\Games\...).

Hi!

Same problem here. Tried everything and have now surrendered to Virtual PC 2007. Installed XP on it and guess what? The issue remains. So I'm pretty sure it's not a Windows 7 only issue. Any ideas what might cause / fix this?

Just to let you know: I've managed to play through Sanitarium. I found that saving often reduces the crash rate a lot! I've just played the last two chapters for about 2 hours and it didn't crash once.
If you save after every major accomplishment, you should be safe. And if not: at least you won't have to do a lot of stuff a second time ;)

Same here. It's not the end of the world to just save regularly and seems to become more stable with time... It's good general adventure-game practice to get used to in any case, a game can crash for any number of reasons.