Random flickering/screen tearing in Windows

I installed Windows 7 and it was working fine. However, a few days ago two things happened:

1) Windows installed an update, and the icons at the bottom of the screen began to bring up small windows showing the folder/program, instead of simply just listing their names vertically, and

2) Windows will suddenly flicker at seemingly random intervals. It's as if all windows are being minimized simultaneously so I can see the desktop background poking through for just the slightest fraction of a second. This happens even when I'm at the Windows 7 log in page.

It's hard to say what causes the flickering. I've noticed that if I keep one window or application open long enough, the flickering stops, but when I tend to move between windows the flickering resumes. It's like Windows is trying to refresh too frequently.

The problem is also particularly bad when I'm scrolling down through a long web page on Firefox.

My malware scanners (McAffee, Spyware Doctor) come up clean.

My graphics driver is the most recent build available.

Does this problem sound familiar to anyone? I don't think this is a hardware problem; moving my screen around doesn't trigger it at all, and the fact it began after one particular update makes it seem like a software problem.

Thank you very much!

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