Bug#600706: gdm3: I can not get into my account if already open (steps to reproduce)

[Thomas R.]

User switching using gdm3 in Squeeze is essentially broken.

It's impossible to return to the first user's logged in session after 
switching to another user in the normal way.

Steps to reproduce:
1. While logged in as some user, go to "System" -> "Log out (user)" and 
click "Switch User".
2. Log in as some other user.
3. When finished, go to "System" -> "Log out (other user)" and click 
"Log Out".
    At this point, the second user has logged out but the first user is 
still logged in.  The current version of gdm3 shows a tick next to the 
first user's name to indicate this.
4. Attempt to log in again as the first user.

Expected behaviour:
Able to return to the first user's already open session.

Actual behaviour:
The first user's open session flashes briefly up on screen, then you are 
kicked back to the login screen.
Repeated attempts to log in to that user's already logged in session 
also result in being kicked back to the login screen after a brief flash 
on the screen.

Reproducible:
Always

Workaround:
Switching virtual terminals with CTRL+ALT+F7 successfully brings you 
back to the first user's login screen.

This suggests the problem is due to erroneously switching virtual 
terminals after returning to a login session.

I'm also using gdm3/2.30.5-4 (same as submitter) and can reproduce this 
each time, on both my Debian Squeeze based computers.

Cheers
Thomas