nt workstation as print server

We have recently upgraded some Win 95 machines to Win NT 4.0 sp5 workstations. These machines are used as print servers for a 100 person firm. It seemed to work well for a couple weeks, then started giving errors such as “Cannot Open Port” or “to many concurrent logins”. Each printer is accessed by 10-30 users. I think that the systems are not dropping connections once people print to them and therefore there aren’t any available spots for new people to connect. Once a system is rebooted, it seems to work fine for a while. Is there anyway to automatically drop these connections or alleviate this problem? Thanks for the help!