Since several mice have not worked, perhaps the the issue lies with the Tablet.
Did any mouse ever work correctly? If so how long ago? Have you done any Software, Driver or BIOS updates since the time that it worked? Have you checked your Device Manager to ensure that all is in order?
I don't know anything about PC Tablets, but I would imagine that the basics are similar.
A Scientific Method approach should be able to yield some sort of positive result.... I hope.
[SIZE=\"1\"]E6400 @ 3.4 , Noctua 120
7900GT @ 670/1680 , VF900
2 x 1GB Patriot 6400 @ 425
WD SATA 250GB
Neo HE 550
P180 / G15 / MX1000[/SIZE]