Resolution of the login screen is wrong on a second monitor

Solution 1:

The login screen in 11.10 uses the default X behaviour for multi-monitors. In most cases this is mirroring, but various drivers can behave incorrectly (e.g. incorrect resolutions or not working second monitors). We have this in 11.10 as the original solution of managing the monitors like the session does had more problems.

This feature is planned to be revisited for 12.04 to make the experience better. The desired behaviour is the monitors run at their native resolutions, have the background correctly scaled/cropped and a user can log in from any available monitor.