Server 2003 connectivity

Hi all:

I have a network with a few Win98 stalwarts that run a program that gets
crabby under XP. Recently, we've started having a problem where, after about
30 minutes of inactivity, the 98 station seems to lose it's connection to the
server and must be rebooted to resume proper operation. The mapped drives
just seem to go away. I've installed a hotfix that is supposed to resolve
the issue but it didn't help. We're using a Server 2003 box as the main
server. Please help!