Wireless multimedia keyboard randomly stops working

This is a bit of a bizarre problem.

I've got a wireless keyboard (Microsoft Wireless Multimedia Keyboard 1.1) that will randomly not work. The wireless mouse that came with it will still work, and I've never had any problems with it. It's just the keyboard.

I googled around and have tried:
-reinstalling the keyboard drivers from the Microsoft website (didn't work)
-hitting both the connect buttons on the keyboard and the signal thing that receives the keyboard and mouse signals and it plugged into my usb port (didn't work)
-swapping the batteries around for both the mouse and the keyboard (the batteries are fine; the mouse kept working but the keyboard still wouldn't)

In fact, the only solution I've been able to find is changing the usb port that the signal receiver is plugged into. Lucky me, my computer has four of them. But even then this solution is only temporary, because the keyboard will randomly crap out on me and stop working again. If I change the usb ports it'll work again (but the keyboard WILL NOT work with that previous usb port again).

... I'd really really appreciate some help. I tried looking for an email I can send this to at Microsoft but they don't even list wireless multimedia keyboard in their technical support area, and under multimedia keyboard they don't accept my product number, so I'm having trouble just emailing them too. :sigh: I can't win.