After a recent upgrade (I do not remember from which version, but the problem
occurs as of release 290), Hudson is unable to connect to our SVN server to
check out the project.

The authentication method is username/password. The project is configured to use
"pangu" as the username, but the administrator of the SVN server reports that
the actual password supplied is "hudson" (which is the owner of the Hudson process).

I've deleted "hudson.scm.SubversionSCM.xml" in an attempt to start again
(restarted Hudson after deletion), and even used a different browser to enter
credentials to avoid caching. The "hudson.scm.SubversionSCM.xml" is recreated,
but yet the wrong username is sent.

It seems that no matter what valid username/password we use for "Enter
Credentials", the username is accepted, "hudson.scm.SubversionSCM.xml" is
updated, and upon building the project the "hudson" username is passed rather
than the configured username.