PC Issues- Graphic Card Linked?

Lately I've been experiencing some weird issues, the first thing I noticed was small red lines on certain parts of the screen which come and go, though they disn;t affect anything on their own. Then I started having random crashes, which seemed to only come when my PC was idle (ex- I'd leave the room and my computer on for 20 minutes and come back to find out the PC had reboot itself in my absence). The funny thing is this issue never comes up even under heavy video card load like playing Company of Heroes, or Starcraft II under full graphics an 1920x1080 resolution, then I always get solid performance and good frame rates.

Now I'm noticing a couple more problems, my PC will sometimes crash if I'm playing several videos simultaneously. It reboots and I get a "Graphics Driver has stopped responding and recovered succesfully..." error. Additionally, videos viewed online will freeze while audio continues and won't play until I move my mouse cursor to "wake them up".

Finally, I'm starting to have issues in games, I recently picked up Dead Space 2 and am noticing it constantly crashing at a certain part of the game(happened 5 times now) and no one else seems to have the problem, so I'm thinking it must be due to my videocard as opposed to fauly game coding.

I decided to update my drivers though I'm not entirely sure if they're actually taking effect, as it stands now my videocard driver is labelled as Version 8.812.0.0 under device manager. Is this the latest version? Do you see any other reason for the issues I've been experiencing?

I've run a fill scan with Malware Bytes, Nod32 and Spybot S&D to try and root out any malware/virus related causes, they all came back clean other than some "suspicious tracking cookies" picked up by S&D.

Here are my specs if they might help:

OS: 64-bit Windows 7 Home Premium

Motherboard: Biostar T5 XE

Processor: i-750 Intel(no-overclock)

Graphics Card: ATI 5850

Ram: 4GB Ripjaws G-Skill RAM

PSU: 700 Watt OCZMSXP

Case: Cooler Master HAF Tower

Hard Drive: 1 Terabyte hard drive(forgot the exact model, I think it's a Western Digital)