intellimouse

here is a puzzler

win98 p3 600 with realtek nic and serial mouse 6 other users attached to 3com hub, everybody happy. Change serial mouse for ps2 type oem wheel mouse and computer boots up as normal no errors except nobody visible in network neighbourhood no conflicts in device manager and tried plain ps2 mouse everything back to normal. Try different wheel mouse no network again but strangely again no conflicts visible any ideas?