Input Not Supported, Acer Monitor

Before everyone jumps to a conclusion, please read.
I have been using a separate configuration file from time to time for a game that I play, in which it contains controls, binds, graphic settings, etc.

I use it from time to time as it usually helps me see, but one day I loaded the game and it said Input Not Supported. The resolution in that configuration is standard, 1024*768. Two weeks ago I had the same problem, oddly enough, and I couldn't figure it out. Finally, I reinstalled the game and it worked. I was assuming there must've been a map/mod or some other file that was getting in the way.

Last night, I reinstalled twice. I did a clean uninstall, reboot, install, and JUST put the configuration file back in. No luck. I had a backup of the configuration file, and still no luck. [I wanted to make sure nothing changed on the config]

I'm stumped.

Nothing to do with the refresh rate? Just a quick guess.