Downgrade the format of a Subversion working copy
Sometimes, when you upgraded the local subversion working copy, but others use an older client to access it, error likes "This client is too old to work with working copy..." will appear.
To fix this, you can consider downgrade the format of the subversion working copy.
E.g. Downgrade to 1.4
# change-svn-wc-format.py /path/to/working/copy 1.4
The useful python script can be downloaded here: http://svn.apache.org/repos/asf/subversion/trunk/tools/client-side/change-svn-wc-format.py