windows key shortcuts freezing taskbar in xp pro

i'm running xp pro sp2, athlon 64 3000+, 1gb ram (don't remember brand), 160gb segate barracuda, 7600gs, ummm, not sure what else will help, as i have no idea what might be causing the problem.

i've recently started running into my taskbar freezing whenever i use one of the windows key keyboard shortcuts (Win + e, Win + d, etc.). For example, if i hit Windows Key + E to open windows explorer, then the windows key, ctrl+esc, or clicking anywhere on the taskbar, all do nothing. however, after it freezes the taskbar, if i right click on my computer, and click explore, it not only opens a windows explorer window, it opens all that i've requested while the taskbar was frozen...so, win+e (freeze), win+e, win+e, then right click, explore = 4 windows explorers.

i've removed a boatload of malware with spybot s&d, adaware, hijack this, ccleaner, regscrubxp, uhhh i think that's all of em. as well as disabled all unnecessary services, programs, etc., from starting at windows startup.
i've watched the task mgr while it's 'freezing' and the cpu load never goes above about 20% or so, assuming i'm not in the middle of anything...and even while my taskbar is inoperable, everything else works fine, no lagging or anything.

nothing has changed hardware-wise since before the problem, and it only does it about half the time, regardless of what programs are running, cpu load, etc. sometimes it does it from the minute i start up, sometimes i'm fine for a couple days.

it's more of an annoyance than a major problem, but any help would be greatly appreciated.