Somehow someone has manage to create two folders with the same name except the case of the first letter (eg "trunk" and "Trunk") which causes the svn update to fail (because windows being case insensitive wont allow the creation of both folders).
How can I revert these changes on windows (and without direct access to the svn server)?
I'm using the tortoise svn client, and the server is Unix (which I'm guess why it allowed both folders to exist).
Use the repository browser to work directly on the repository; either delete the directory directly or view the log and find the revision which introduced the problem and revert changes from that revision.