In case of the lock, it may be just an unclean state. So, you can first, optionally run:
sudo svn cleanup
Then you can reset the permissions on the metadata files (in older Subversions there were many
find -name .svn | xargs chmod -R 777
If you have spaces in names (which is a bad idea), you can still run:
find -name .svn | while read f; do echo $f; sudo chmod -R 777 "$f"; done
I'm not sure about the durability of this solution (if SVN won't change the permissions back, after some operations), but then you just need to reapply this solution.