I have a Polaris PB4 booster pump, installed late July 2006, vacuum was running for an hour tonight but I noticed it wasn't moving across bottom of pool normally--wheel was skipping. I shut things down and noticed the rubber tire partially slipped off the wheel and was jamming against side--hence the skipping rotation of the wheel. After fixing tire, I then went to turn on pump again and got an electrical humming sound, but pump not doing anything mechanically and not pumping water. The side of booster pump was pretty warm. I shut off the pump and turned it on again and got nothing--no humming or anything. I tried again later, got the humming but then heard a click and it went silent again. Please advise, thanks!