Okay, you guys made me do it. LOL I replaced the old mouse and USB Dongle with new ones I had in reserve (same model), and I still have the same problem: After logging on, I have to remove the USB Dongle and reinsert it to make the cursor active.

I don't see how dust could have gotten into the USB port, seeing as that dongle is in it all the time. I have a feeling this might be a glitch caused by a recent update.