Comment 2 for bug 235956

that is essentially only reverting the fix, -ac means *everyone* in the world can connect to your display and do keylogging, take screenshots etc. -ac drops any support for xauth (.Xauthority) and all security completely...
the only breakage i'm aware of with the current patch is if you force he usage of NFS (not a default) and /root is not writable to create the xauth cookie.
are you using NFS ? if so, there is a fix in the most recent ltsp upload in hardy-proposed.