bizare network behavior

[James McNeill]

g'day everyone.

Somewhere on my network something is making my life very hard.

Windows client talking TCP to Linux server. At first all seems fine, but the
time between packets gets slowly greater and greater until the connection
grinds to a halt. It impossible to transfer more that about 50k in any given
TCP session. But, as soon as the connection is closed and re-opened, the
packets flow freely again, breifly. It seems to be happening to all
protocols, POP SMTP SMB and FTP. Other machines on the network seem
unaffected.

I've never seen this before, can anyone help?
thanks in advance,
-James