Reasons for 400 Bad Request on committing which don't involve proxies?

For a few weeks now (I can't pinpoint exactly when), I have been
unable to commit to several of my repositories, but only from one
workstation. I have gotten both 403 and 400 errors, the 400 error
being the current one.

svn: Server sent unexpected return value (400 Bad Request) in response
to MKACTIVITY request for
'/Repos/Projects/!svn/act/451cfa98-d507-4b43-8f05-9ebdce0a1e5f'

Every search I do gives the answer that it's a proxy not allowing the
WebDAV methods through. But this only happens for my workstation (Win
XP, SP 3), on our internal network (no proxy/firewall between me & the
server). No one else in the office has had any difficulty. It happens
regardless of which client I use - TortoiseSVN (latest 1.6 release),
CollabNet command-line (1.6.6), or Subclipse. I can't even perform
operations directly on repository URLs via the TSVN Repo-Browser.

I've tried changing http-library from neon to serf, but that just
results in the following:

svn: Commit failed (details follow):
svn: Unspecified error message

Windows Firewall is disabled. I've rebooted. As far as I know, no
changes have been made to my antivirus, but I can't disable it myself
and requests to disable it for testing purposes aren't received
warmly.

What else can I try here?
Received on 2011-08-26 21:09:19 CEST