I apt-get upgrade ; apt-get dist-upgrade Jaunty every couple of days.
Since yesterday I am not having the reported problem any more. Now when I log in the resolution is set correctly (in my case 1024 × 768 on the laptop panel, 1680 × 1050 on the external monitor relative-positioned above the panel).
I will report back again if the problem reoccurs, hopefully with more information about the circumstances under which it occurs.
This may not be very useful information, but ...
I apt-get upgrade ; apt-get dist-upgrade Jaunty every couple of days.
Since yesterday I am not having the reported problem any more. Now when I log in the resolution is set correctly (in my case 1024 × 768 on the laptop panel, 1680 × 1050 on the external monitor relative-positioned above the panel).
I will report back again if the problem reoccurs, hopefully with more information about the circumstances under which it occurs.