Disconnecting AS/400 Connection

Setup:

PortServer TS2 with a USR Modem attached to it
Win NT 4 server configured to dial out via the modem
Client Access used to connect to an AS/400 via a mapped drive

Process:
Drive is mapped to the AS/400. Call is placed with the modem, files are D/L and then copied to the AS/400. Easy enuf.

Problem:
Modem connects to the remote server(s). After a time of being connected the AS/400 connection drops the drive mapping. It cannot be reconnected without a reboot.

Any ideas?

How ofter does the disconnect happen? Is it consistent?

Is the PortServer pingable when the disconnect happens?

What version of the RealPort driver are you using?