Error: svn: E155004 Commit failed (details follow):
svn: E155004: Working copy '/path/to/repo' locked
svn: E155004: '/path/to/repo' is already locked.

find . -name 'lock' -exec rm -v {} \;

The problem is that with Subversion 1.7 this doesn’t work anymore. The good news is there is a better way to do this – and what it appears I should have been doing this all along. All you need is:

<-- linea di comando -->
svn cleanup

<-- interfaccia -->
1 - Select the project
2 - Right click on the selected Project
3 - Team -> Cleanup

If you’re interested, the man page is available in the SVN book.