Their router has what is called a "firewall" that blocks UDP packets, which
is what CU-SeeMe uses to send its data. They might even block only UDP port
7648. The following info is straight from the readme.txt file:
CU-SeeMe uses the UDP protocol. This is different from most TCP/IP
applications which use TCP. UDP is used by NFS (Network File System)
and PING and a few other programs.
CU-SeeMe uses UDP socket 7648. Some network providers have "firewalls"
installed that prevent UDP traffic such as CU-SeeMe from flowing. Some
of these providers are willing to remove the firewall for you if you
ask, some are not. There is more information about firewalls in FAQ.TXT.
Bill Woodland (email@example.com)
Squeek on Undernet IRC
Channel Manager #CU-SeeMe