It was happening on the razer mouse I had too, one of its annoyances.
This generic one is doing it all the time too, every day, every mouse button included the right click and middle click.
And every mouse I've hookup up does it.

Have any of you guys encountered this prob?
So far Ive done tried fixing the button a 100 times over.
New try for a fix was to set the double click speed in the windows mouse cpl, hoping this will fix it.
Err just checked and it still happens alot.

Ok, hm...
On its own usb port, instead of through the keyboard, still happens.

Ive got other usb probs too, but I figure those are software issues.

I don't know where my usb to ps2 adapter is, I've got 2 or 3 of them somewhere.