Loosing Network Connection

We are running NT 4.0, SP6 on a 10/100 network. Workstations are W95/W98 with 3Com nics. When users log into the network, their login script maps a drive to J.

We are having a random problem of workstations dropping their network mapping for noapparent reason. The connection will drop even if the user is using files on the mapped drive.

Any thoughts?

TIA,

Byron