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.
I'm replying to an old message I know, but I just installed Sanitarium, and I think I had the same error when trying to launch the game.
In my case, the fix was to go to Sanitarium shortcut properties => compatibility, and enabling "Run this program as an administrator". After that the game lauched and ran fine. I've now played somewhere to 2nd chapter without issues.
Specs: Lenovo ThinkPad T400 laptop, Windows 7 64bit.
So could it be that for some reason that compatibility flag was accidentally removed from your game, hence it didn't work anymore? Then again, in my case it wasn't there after installation, I had to go enable it.