All Available Drives Mapped

We have serveral people that all their available drives map to one drive. They may have a: c: d: o: x: and y: mapped at login and then some time during the day any spare drives are mapped to, for instance, the x: drive. Something causes any drive that is available between a: and z: to take the x: drive mapping. This may occur at different times of the day. I have not seen this at login. The users have NT4 sp6, Office 97 and Windows NT login scripts map network drives. One user had it happen when he would go into an Excel 97 document. Any suggestions?