It's as simple as I said in the title. About 60% of fangames fail to start. Affected games include the entire Kamilia series, I wanna Kill the Guy, I wanna find my destiny, and more. When starting certain games (including the Kamilia games), I receive the entirely unhelpful error message "Unexpected error occurred when running the game." and the game exits. With others (such as I wanna find my destiny), the game simply sits at a black screen while the music plays and slowly allocates more RAM while not responding. With the other 40% of games (including the original I wanna be the guy, I wanna be the Boshy, and I wanna sunspike), the games start up and behave exactly as expected.
I'm currently running Windows 7 Professional, 64-bit. With no useful error messages of any kind and standard methods of fixing similar errors (compatibility mode, administrator mode, etc.) not working, I'm not sure what the issue is or where to even begin on finding a solution. Any assistance is appreciated, and any necessary information for fixing the issue can be provided.