Tip: If you have a wireless USB mouse and you have the dongle plugged into a back USB port of your desktop computer, and the mouse is having a dodgy performance, skipping, not clicking, jumping all over the place... if you have a front USB port, plug the dongle into that instead and your issues should clear up. I don't know why, but I'm thinking that the electronics inside the computer (possibly a wireless internet connection?) is causing havoc/interfering with the wireless signal your mouse needs to do its thing.
That's what happened to me.