Comment 12 for bug 196464

I have seen the same problem (I do not know if it is related to GDM, but this is with hardy).

At the moment it's particularly bad; .Xauthority reverts to root:root within a second of changing it by hand to user:user.

It seems to be atieventsd which is the trigger of this (but possibly not the cause; I tried strace on it but it didn't seem to call chown itself). When I stop it, .Xauthority stays as user:user.