Open Design Engine

We've been experiencing an issue with older repositories where they are accessible via Subversion, but when viewing them from the Repository tab, a 404 (no content) error is returned. Note that newer repositories did not have an issue. Looking at the server logs, a message like the below was being logged:

...
No close tag for /lists/list
Line:
Position:
Last 80 unconsumed characters:

Output was:
 <?xml version="1.0" encoding="UTF-8"?>
<lists>
<list
   path="https://opendesignengine.net/svn/ode">

Rendering template within layouts/base
Rendering common/error (404)

A Google search turned up a number of other people seeing this error as well, but in their cases it was new repositories, not old ones. In addition to the error message we were seeing, all of them were also stating issues with SSL (either via HTTPS or SSH). This thread on the Redmine forums in particular was of help: http://www.redmine.org/boards/2/topics/11896, which led me to running

svn list --xml "https://opendesignengine.net/svn/ode"@HEAD

This prompted me to accept the server's certificate because it was failing to be validated by the local SVN client, just as others were reporting. Once I had permanently accepted it, everything started working again. I'm still a little perplexed as to why newer repositories had no issues, but I suspect it had something to do with a partial update when the server's certificate was updated last.