Game goes wierd for no reason.
I'm playing on Civ 5, and all of a sudden part of the screen will go really wierd, mostly black, grey and orange streaks, and lag the game up really badly. But it acts like a wall, blocking everything out on the other side. I can send the camera through it, and it will be look normal on the other side, but the lag is still there. If I switch to the tactical view, and back, it's still there. How do I fix it?
This might be caused by video "glitching" (texture or model corruption, I'd guess), often seemingly as a result of overheating or power fluctuations (usually heat). What sort of video card do you have? Have you checked its temperature while playing?
As a side note: I know exactly what you're talking about. I had the same issues with the game with my old(er) system. It used an 8800GTS/G92 and was likely to have this happen when it got a bit too hot (about 80C for me). Sometimes reloading the game would help.
With my new system I haven't seen this issue.