One day you're happily committing and updating your code in SVN, the next day you end up in trouble. It all started when suddenly my svn-client started moaning that it was too old. From that point on, no update or commit was possible. I googled on the error and it turned out that the svn 1.4 version used an incompatible format. My working copy must have been changed on the fly. And of course I still had 1.3.0. It took a while before I found a OS X binary package of the svn-1.4 client. Thanks Coding Monkeys!