Ubuntu – Problems with subversion (in gnome keyring, maybe), user=null

I'm having a problem with my subversion in Ubuntu, and it's happening only on my computer, my colleagues are working fine. It asks for password for user "(null)":

Password for '(null)' GNOME keyring:

entering the password it shows:

svn: OPTIONS of
'http://10.0.203.3/greenfox':
authorization failed: Could not
authenticate to server: rejected Basic
challenge (http://10.0.203.3)

What can be causing that (again: it's just on my computer, the svn server is ok).