An interesting thing I have to tell you, maybe it's gonna help one or the other with a similar problem:

For months now my system was completely freezing time after time when playing Nexuiz. It never happened at any other instances (of course, Nexuiz is what claims the most output for my PC). The last weeks it happened more and more frequent.

Funny as it is, it didn't happen anymore when changing from nexuiz.exe to nexuiz-sdl.exe which I didnt like too much because of a few drawbacks I dont want to mention at this point. Talking to some knowledgeable people I decided to change my old Enermax Power Supply to a new one, although there wasnt any measurable problem with it. The thing, it was not the newest anymore, I bought it about five years ago.
First I couldnt believe that there are some parts in it which get lame after a time. And, what does it have to do with it when nexuiz-sdl.exe is running??

BUT: Guess what, both nexuiz.exe and nexuiz-sdl.exe are running properly again

So never forget, the power supply is a very underestimated aspect. In its very aboriginal sense if you want power, you have to give it to your rig! Spend some money on a decent PSU, provide your PC the full power so your PC can provide it to You!

So you mean nexuiz-sdl.exe does work fine even without gl_finish 1 now? That would be good news but its also kinda horrifying that a bad PSU can do such things
Well thats a reason to buy a new computer every year