After running Win 7 for some unknown period of time, the taskbar icon highlight starts to stick. If I restart or kill explorer.exe and relaunch, it goes away.
I found that Shift-Right Clicking on any taskbar item brings up the pre-7 context menu and after it's dismissed, the highlight is not stuck any more.
No idea what's causing this though, but I hope it's a monthly-update-fixable type of bug.
Also, check out some useless replies from Microsoft: