Comment 102 for bug 331369

Confirmed, problem still occurs on 11.10 (I'm on ATI binary drivers).

Maybe it's somehow related to this one:
https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/742544?comments=all

In both cases 'primary' flag for monitor is ignored.
Dash goes to most left monitor.
Notifications go to the most right monitor.
With multiple configuration screen no matter how one would connect and set them even scarifying favorite arrangement. Still notifications will be on the other monitor than dash.

That's a true no-go.