Subversion / Apache griefs: can’t commit, MERGE failed

Installed Subversion. Configured Apache to run as a Subversion server. Seems to work. I even tried some WebDAV applications (davfs) on it. Work. Not perfectly (some strange errors), but it does work. Until I tried to checkout, modify and commit with SVN itself: svn: Commit failed (details follow): svn: MERGE request failed on ‘/’ svn:…