If you uses Cygwin and you happens to also include the svn package when you install Cygwin, you won't be able to release your project because the Cygwin svn is broken.

You will get error messages similar to

[INFO] ------------------------------------------------------------------------
[INFO] Unable to commit files
Provider message:
The svn command failed.
Command output:
svn: '......' is not a working copy

The solution is to just use a windows svn client instead of the one that comes with Cygwin. The Cygwin svn is just a re-linking of the linux svn client with some wrapper linux API of windows (I think), which in this case is having trouble resolving windows path.

The problem is also documented on http://jira.codehaus.org/browse/MRELEASE-146