svn doesnt work on one of my 3g connections

Hi,
I have a rather odd problem where I cant use svn with one of my 3g connections.
My main connection is a generic 3g usb modem which everything else
works fine over (although slowly). I can ping the remote server fine
(~430ms) and tracepath seems to be sane. If I try svn up it will just
do nothing (I cant even ^C it). If I connect with my phone it all
works fine. (Both connections are the same cell towers but apparently
different routes out of the country)

Attached is ping and tracepath for both connections (different local
computers though it doesnt make any difference).

Any ideas what could be the issue?

Cheers
Jonathan

P.S

 $ svn --version
svn, version 1.6.6 (r40053)
   compiled Dec 12 2009, 05:06:12
$ uname -a
Linux thor 2.6.32-24-generic #39-Ubuntu SMP Wed Jul 28 05:14:15 UTC
2010 x86_64 GNU/Linux