Fairly frequently I encounter a problem when trying to access my Windows7 taskbar. I get an hour-glass that never goes away unless/until I click enough to prompt Windows to announce that Explorer is not responding, asking whether I want to keep waiting, close the program, or restart. Whether I choose to close or restart, the response is the same: I can use the taskbar again almost immediately, though about 50% of the time the problem will reoccur within 15 minutes.
I am running Windows7 Home Premium (64-bit edition). I experienced the same problem while running Windows Vista before upgrading to Windows7 (6 months or so ago). It was a significantly less frequent problem during the first couple months after upgrading. but the frequency has increased. Running the GIMP graphics editor seems to be the most frequent way to encounter this problem (80%+ of the times I run GIMP, I experience the problem at some point), however I've experienced the same problem during sessions in which the only app I use is Chrome. The system is Toshiba Satellite laptop, with 4GB of RAM and a 2GHz AMD Turon 64-bit processor.
What could be causing this problem? Short of a full-blown reformat+reinstall of Windows, what could I do to fix it?