If you find that the location to a subversion repository has changed, do this:

svn switch --relocate http://textpattern.com/svn/repos/current/textpattern http://svn.textpattern.com/current/textpattern

Where the old url is http://textpattern.com/svn/repos/current/textpattern

And the new one is http://svn.textpattern.com/current/textpattern

To see if it worked, do this:

svn info | grep URL

And you should see something like this:

URL: http://svn.textpattern.com/current/textpattern

(source: Switching a Working Copy)