or resetting your wireless mouse. (I have a small wireless Logitech mouse at work and it has a reset button on the bottom).
Try those two and see if your problem still exists.
If it still happens on a wired mouse - you could try changing the way users log on (to the option of them typing their user names)
If it doesn't happen on the wired mouse but still on the wireless after you reseted it, try changing the battery. If no luck still then maybe it is time for a new mouse??
Sometimes when I start up Windows xp pro, the mouse will move over the user and admin accounts, but they will not highlight. I have to restart, sometimes 3 or 4 times to get them to "highlight". Any idea on how to fix this.
Windows xp pro
1 Gb ram
256 MB Nvidia card
Intel 2.54 GHz processor
Logitech wireless mouse. (yes I have latest drivers)