1) Are there any indications in the Windows event viewer; i.e. IP Address Conflict? (Windows) Start menu --> run --> eventvwr
2) Are you using DHCP on the XP Pro box? Does it still happen if you statically set the address.
3) Have you tried manually setting the WinGate servers IP address in the WGIC?
4)
This client erratically loses Internet, Mail and Network printing until the WIC is reset and the PC rebooted
What about if the PC is just rebooted, without resetting the WGIC?