Netport Printserver Intermittent

Have Netport Express 10/100 (2)port print server on NT network. Only two win98 workstations to print directly to print server. Installed drivers on workstations to print directly to the print server. Works fine for awhile, then connection to printerlost. After awhile it comes back. Print server settings: speed=autodetect, static ip assigned, bidirectional comm=off. What am I missing?