help analyzing scp problem on FC5

[Peter Horst]

Hi - I'm having trouble figuring out how to start diagnosing a 
(software) problem on FC5.  Here are the facts:

I'm using WinSCP3 (v. 4.0 beta) to transfer binary files (3-4 megs 
generally, mostly .mp3) from a Windows XP machine to my (yum updated) 
FC5 machine.  At some point in the transfer process (a different point 
each time, but generally after several Mbs have been transferred), I'll 
get a "disconnected by peer" message on the Windows machine, and the FC5 
machine will get kicked off the network - that is, not only does it 
become impossible to reconnect to it via WinSCP, but any existing SSH 
sessions will disconnect and cannot be restored.

Unfortunately, this requires a reboot of the FC5 machine, as I am 
running it without a monitor/keyboard.

The openssh-server version is 4.3p2 (Release 4.12.fc5).

How would I go about collecting the information needed to figure out 
what's going on here?  I have recently replaced virtually all relevant 
network cabling/hardware, so I don't think it's that...

Any help greatly appreciated.