System Acting Funky -- Can't Maintain Previously Stable OC, Artifacts/Vertical Lines

Hey Guys,

Up until recently, my system was operating fine and has been for 8 months. It's a 1090T overclocked to 4 GHz (200x20). Then one morning, the system spontaneously restarted under load, and I was never able to get back into Windows. It would either restart back to the POST screen or stall on a primarily back screen with five or six cyan dashes in the top left hand corner after the Windows 7 boot logo would disappear. Going back to stock speeds and voltages didn't make any difference. While I was making many loops restarting, I noticed sometimes at POST it would have a garbled up screen, or the Windows safe mode menu would have two bold vertical pink lines.

I ended up reinstalling Windows, and the system isn't exactly 100% back to normal. I use my rig primarily to play StarCraft 2, and at times, I've noticed the FPS drop to 10-15 frames. I play on Extreme settings, but this was never a problem before. I tried to even bump it down to Medium settings during the game, but it didn't make a difference. It wasn't until I restarted, that it went back to normal. Today, I tried to revert the system back to its previously stable overclocked settings, and it's no longer stable. The symptoms that I saw earlier when my Windows went FUBAR are back -- intermittent garbled up POST and BIOS screen, Windows safe mode menu has two bold pink lines, and since I have dual monitors, my right screen shows the boot logo/menu before the left, but when things are screwed up such as showing those pink bars or unable to get into Windows, I don't see anything on the right monitor at all. I've also tried upgrading the BIOS to a newer version (F7e).

Another weird issue that has always happened from when I had this system is my USB systems would sometimes get "stuck". My gaming headset is detected, but it won't actually play audio until I unplug/plug it back in. It has also affected my Razer mouse, where it won't move until I unplug and plug it back in.

Any clues as to what it may be? I'm thinking it's either the motherboard, video card, or PSU. The issue is this is my only system, and I don't have another system or friend to swap parts and isolate the issue with.

The system at stock speeds/voltages can pass through Prime95 and FurMark fine. The core temperatures showing in HWMonitor never exceed 50 degrees under load. GPU temperatures while playing StarCraft are in the mid 70s and as high as mid-80s when running Furmark.

System:

1090T
Gigabyte 890FXA-UD5
Corsair H80
XFX Radeon HD 6870 900MHZ 1GB (Stock)
Corsair 60GB SSD
Corsair TX650W 650W
G.SKILL Ripjaws X F3-12800CL9D-8GBXL 8GB 2X4GB

Here are the two pink bars at the Windows menu:

I think I've partially resolved the issue:

1. The performance issues were BIOS related. The updated (and unofficial) BIOS version wasn't exactly stable. I noticed in CPU-Z that my CPU was constantly throttling itself down to 800 MHz, however while it was under load, it seemed to remain constant at the clock speed it was supposed to be at, so I ignored this since upgrading the BIOS. While I read this was an issue with my motherboard, I was never affected by the issue before. I also noticed my voltages were constantly fluctuating. It wasn't until today that I went back to my old BIOS version, and behold, my performance is now back to normal.

2. Prior to finding out about my BIOS issue, I also addressed some heat issues on the northbridge and my GPU by replacing the paste with MX-4. The northbridge temperatures are now 10 degrees cooler, and the GPU temperatures also idles lower, but during load still spike up to about the high 70s. But this is due to the controlled fan speed via Overdrive.

3. The artifacting and vertical lines do still periodically appear, but it isn't happening every time it restarts. I've also managed to revert back to my original overclock settings, with even lower voltages.

Thanks everyone for the help and suggestions.