BG Process Keeps Taking Over And Bumping Out Of Active Windows?

I can be in MS Word, After Effects, Surfing or ANY OTHER PROGRAM, and not click out, but be just working away and all the sudden SOMETHING (your part) causes my active window/program to go like it was a background process. could be in the middle of typing an email, and in the middle of a word and I can get half of it typed and then... BOOM! I'm out. The program DOES NOT close, it just acts like I clicked away to the desktop or another program.

Then I have to click back on my email and can resume typing for a bit. This happens every 5 minutes or so (haven't timed it). When it clicks itself out, it doesn't really go anywhere that I can tell, but something is definitely making my active window/program become inactive. I'm assuming it's some background process, but I don't see anything pop-up or blink or give me ANY indication at all that it has taken the active position.

I'm not sure how to even phrase this question since I don't know what is really going on. But it's driving me crazy in my video editing program (Premiere) especially since I'm in it about 15 hours a day. So it's happening, as you can imagine, 5-10 times an hour during my playack.

In fact, just at this very moment it did it again while writing here. My Chrome page became inactive and I had to reclick right here to continue writing.

I've had probably 50 computers since Windows 98 and I've never seen this before. And of course this has to happen on my big edit monster that I'm on all day. The system is a dual Xeon x5680, overclocked to 4.5Gzh, with 48 GB ram. I'm running on a EVGA SR-2 motherboard running the latest bios (as of 2 months ago). Runs like a beast in everything, very stable, just this annoying problem that keeps surfacing all the time. I'm running Win 7 Ult 64.