USB device non-recognition.

I run a Windows XP machine. My primarily periopherals are a Lacie external hard-drive, a Maxtor portable hard-drive, a Canon Pixma MP600 printer, and my iPod. It used to be that all of these devices worked perfectly. Lately, however, each of them has taken to giving me the "USB device cannot be recognized, it may have malfunctioned or blah blah blah..." message popup from the task bar. All of these devices still work on other computer. In addition, my mouse will occasionally loose and regain recognition during use, offering the "ba-dunk" recognition / unrecognition sound 2 or 4 times in quick succession, sometimes even resulting in the mouse / keyboard remaining unrecognized until I reboot the machine. This, however, may be unrelated, as I recently purchased a new mouse, and I don't think it's occured again since.

No effect, I hate to say... although the registry clean did a lot of good for the compy's overall health, I think. In any case, I still have 2 "Unknown Device" listings on Device Manager under the USB tab. Any ideas?