I have owned a wireless "Mighty Mouse" for less than 6 months, and I loved the product. Yesterday, after I changed the batteries (same Lithium batteries), the small trackball on top stopped working. Everything else works as it should. The batteries are not bad; they read 100% on the iStat pro widget. This is the first mouse that has ever failed in 15+ years of computing. What gives? Has anyone else seen this kind of problem?