Mouse Quits

I have just installed PAC on a Maxtor Mini One Touch III - 100 gig. I have it plugged directly into an HP NW8440 w/ 2 gigs RAM running Windows XP Pro Build 2600 xpsp SP2. I have disabled the on board touch pad because I have a Logitech MX500 mouse and Summagraphics SummaSketch III tablet pluged into it. The mouse (USB) & tablet (RS232) are plugged into an HP Port Replicator. When I start the PAC menu I can usually load one program without any problems. After that ever time I load a program the mouse will just stop working. I can unplug/plug the mouse and it will start back up again. The tablet works first time every time. I have looked over the Forums and have not found anything to help. I have also installed all the patches and updates (beta, etc.) that I can find on the site. Can you help with this problem???