1. Not my gaming comp, but still worried about it. When I play games in Steam [TFC only, others crash computer] I get a perpetual lag about every 10 minutes the games freezes for 1 or 2 minutes. Now anything could be happening to me, so I just hope I don't get fragged too much or I wasn't holding the flag. Sometimes it freezes for a while longer like 10 minutes, but it always comes back on. I've re-installed Steam and deleted all local content many times, but it's no help. ???
2. While surfing the net [only Mozilla FF does this] the screen blacks out and then comes back with a bit of a flicker. I don't know what promts it to do so, but it just does. I've checked the cables and they're tight. Any ideas?
It might be the video card going out or the processor. They might be over heating :/
Yea, I had the same problem with my old computer. Turns out the problem was my power box fan was busted, but I dont know if thats what you're problem is.
I had a similar problem like this a long time ago. It was the power supply and the video card. If you have spares of these, try putting them in and running the games.
And only FireFox does the screen thingy? Odd. You've definitely got a problem there.
try reinstalling firefox and see if it still flickers