Terminal Server with Citrix Metaframe

I have 8 people working out of their homes using Terminal Server. We are running various applications, but occasionally one of them will “lock up” and the only way to get that station reset is to re-boot a router type box by Perle Systems. This is what they use to RAS into our network. We are running TCP/IP and NetBIOS and must run both. Any help on the lock-up would be appreciated. The application that appears to lock on TS is a custom app. that we created. Others running sessions at the time of lockup do not seem affected only in that I must get them to log off the network so I can re-boot the Perle unit.