Internet lockup

[Gordon Gallup]

Greeting All,
   I have a new e-machine T6420.  It is connected to a hub with three
other machines and the hub is connected to a Siemans DSL
"modem-router".  I installed FC5 on the T6420.  The behavior is
somewhat flakey, but it appears that ssh and sftp (particularly the
latter) break networking if I attempt to send too much information. 
It appears to require a reboot to re-estaablish contact. Fiddling with
the inetd.network script does nothing I can detect, although it thinks
the network is up.  Before the death, pinging works fine all around
the machines connected to the hub and also to my office machine across
town.  In addition, Firefox works for a while, but I can't say yet
just how long.
   Attempting to connect with the kio-slave 'fish' never works.
Thanks for any help, GAG