Windows – Chunks of tooltips get stuck, where the screen isn’t refreshing, I guess. (Windows 7 Professional x64, 1-2 monitors)

Here's a screenshot:

It happens a lot, not always. This screenshot was taken after less than an hour of browsing web, searching for something desperately, a lot of mouse movement, plus working on something else, don't remember what software. If I'd press start, for example, the whole top area would get cleaned.

It doesn't happen only near the taskbar, for example, if a tooltip from a software would start showing up while I'd use alt-tab to switch to another application, then it will still show up and stay there on the screen until I'd move my mouse over it.

Usually, I reboot my laptop only when I'll update my Windows, in other cases I'll just put it to sleep or hibernate. I often switch between 1 and 2 monitors setup. Sometimes I play video games in fullscreen.

This problem has been there since I installed my copy of Windows, a few years ago, I believe. Googled then, didn't find anything, googled now, still nothing. It's not an urgent matter but it got me too curious already.

some specs: Windows 7 x64 Pro – up to date; Acer Extensa 5630g laptop, ATI Mobility HD 3650 (original driver that came with the CD, for my laptop; Please don't tell me to update since the new drivers can get really really buggy), Intel core2duo T5800

EDIT :

• Added bounty.

• Please offer an explanation as of why is this happening, and a solution if it exists. I'm not looking only for a way to hide the problem.

• Just a reminder: chunks of tooltips get stuck on margins (as seen in the screenshot), also, a whole tooltip may get stuck in the center of the screen if I switch fast between applications.

EDIT2 :

• Three days remaining until I have to award the bounty and as I don't see any trustworthy answer, at least guide me to where else I could ask this. My Windows copy is a MSDNAA licensed one, I got the key for being a student in a Romanian faculty that is registered in the program. I'm not sure I have any other official support from Microsoft except their representative in my faculty whom I can't reach in the next few months to, maybe, a year from now on, and I'm not sure he'll be able to help me whatsoever.