Subversion 1.5 merge problems

Last days we have had several problems trying to merge two branches using subversion. I wanted to merge trunk to modularity but I always obtained this error:

svn: Working copy path 'lib/runtime' does not exist in repository

This happened using any merge command (svn merge modularity, svn merge trunk@r1 trunk@r2…).
It seems to be related with subversion issue 3067 and the only way to make it work was checking out the svn branch that solves this issue compiling it and using it to do the merge. The steps to do that are:

1) svn co http://svn.collab.net/repos/svn/branches/issue-3067-deleted-subtrees/ svn-mod
2) cd svn-mod
3) ./autogen.sh
4) ./configure
5) make

After doing the merge using that svn client the working copy cannot be used anymore with the old svn client.