Subversion: Can't move... Permission Denied
With the repositories I manage, the repository contents themselves are owned by apache:apache. Trying to do something as root without using sudo -u apache usually creates this situation for me. A good chown -R apache.apache {repo root} will usually fix it, as you indicated.
My guess is that you performed some function via the filesystem as someone other than root.
Turns out we were just missing group write permissions on some of the subdirectories in the remote repository (revs, transactions, etc.) Still not sure how they got mucked up in the first place, though.