For future-Howard (and team), how to fix the error from SVN “your .svn/tmp directory may be missing or corrupt”.
for /R /D %i in (.svn) do if exist "%i" mkdir "%i/tmp"
Open CMD, cd to the SVN directory then run the above command. It will place a new tmp directory inside each .svn directory.
After you run the command, an svn cleanup should succeed.