svn always fails with E120171, but only from some clients

Hi there,

On some computers only, 'svn info' is always giving:

svn: E120171: Error running context: An error occurred during SSL communication

when connecting to our own svn server. This worked previously, but stopped working (I think) after our self-signed certificate expired and was therefore replaced. First we replaced it with another self-signed cert, then we replaced it with a purchased wildcard cert.

- I reproduce this with svn 1.8.10 (Wandisco binaries on OS X) on the client.
- Server runs 1.7.18 (Wandisco binaries on OS X).
- I have deleted ~/.subversion on the client, no help.
- I created an entire new user account on the client machine, no help.
- visiting https://my.server.com/path/to/repository in a browser (tried several) prompts for authentication, succeeds, and shows the expected files.
- I ran "openssl s_client -showcerts -connect <my.server.com>:443" and it reports at the end:
  "Verify return code: 0 (ok)"

I'm now feeling pretty stuck. :( Any suggestions on what this problem is, or how I can diagnose it further?

PS: First post to this list, please be gentle. :)

Thanks,

-- 
____________________________________________________________
Sean McBride, B. Eng                 sean_at_rogue-research.com
Rogue Research                        www.rogue-research.com 
Mac Software Developer              Montréal, Québec, Canada