My Microsoft Intellimouse Explorer started to have button issues a week or two ago. It wasn't clicking. Then earlier this week it started tracking weird as well. Prior to the tracking problem, I wrote Microsoft and told them, and they agreed to send me a new one.

But they sent me the wireless version instead. Score. Good mistake. It's physically the same mouse, just no wire (not that it ever bothered me anyway). I'm comfortably clicking again.