Using the new Eclipse version 3.4.0 and its subeclipse plugin, I found that my linux svn client has been too old:
svn: This client is too old to work with working copy '.'; please get a newer Subversion client
So, I have followed cylindric.net instructions installing via apt-get the 1.5 version of svn client: it works fine for me.
Thanks to cylindric.net
[...] for instructions I came across this blog linking to another blog, but horror of horrors the link was dead! Well, thanks to Google’s page [...]