The same thing just happened to me with saved games from Quake II MP: The Reckoning. The only explanation I could find for this error message is that it typically comes up when Quake II has been patched to a higher version, thereby preventing games saved before application of the patch from loading. Unfortunately, this explanation does not seem to apply to me as I did not patch Quake II after saving the games. I am stumped and hope someone can help.