WJL's final commit of the day failed yesterday, because of a hash sum mismatch. We were unable to solve it last night, but started again this morning. My guess is that it was caused by a corrupted .svn folder on the local machine, or by a corruption on the server. In any case, the only solution was to svn-delete the whole folder, svn-add it again, and then copy backups of the files into it and svn-add them. Weird.