I can confirm this bug. Here is a screenshot of the error message I get when trying to run gdmsetup on Ubuntu Dapper Beta (upgraded to from Ubuntu Dapper Flight March 10 2006 64bit) http://img280.imageshack.us/img280/1095/screenshotgdmsetup5gc.png -- can't start gdmsetup, error https://launchpad.net/bugs/42080