It seems my ubuntu running box has crashed and first my shadow file was empty then SVN had its own problems. It pays so much for one to be patient.

Useful commands:

svnadmin recover /var/svn/repo

svnadmin verify /var/svn/repo

• http://svn.collab.net/repos/svn/trunk/subversion/libsvn_fs_fs/structure
• http://archives.devshed.com/forums/development-94/svnadmin-can-t-read-length-line-in-file-1832366.html