I have no problems whatsover with tuxracer, but with teeworlds. And according to the crash message this has less to to with openGL but with the x message queue that somehow gots fucked up.
And this is not only with the screensaver, it can happen whenever teeworlds loses focus. This can happen for a various of reasons of more important things going on on your desktop other than teeworlds. Hitting Alt-Tab a few times is a method that will raise this error within a short time.
Eitherway, as long this problem persits out of whatever reasons and whoevers fault, having an autosafe feature one would think would actually be close to a no-brainer. [Also I once send in a patch that would use a backup file during safe, yoo do not clompeltly lose your map if teeworlds dies during safe. Also out of whatever reason, even if it powerfail, currently teeworld will delete your file in that case]