Switching back and forth between 2 users does not work

[Huygens]

Binary package hint: fast-user-switch-applet

Scenario:
 - login with user A
 - launch an application (just to make sure it is there when switching back)
 - use the Applet to switch to user B
 - launch again an application (just to make sure it is there when switching back)
 - check that user A is displayed in bold in the fast user switching applet
 - switch back to user A
(if it worked)
 - check that user B is displayed in bold in the fast user switching applet
 - do a 'ps waux' and see if the application you launched as user B is up and running

Where does it break?
Two places:
 - sometimes where it is written "(if it worked)", I get a blank screen and using the Ctrl+Alt+Fx does not change anything. Only Ctrl+Alt+Del or Magic Sysrq tricks work to restart the computer (note that I do not know how to restart just the X server with Magic Sysrq)
 - sometimes after I switched back to user A, I can see that user B is not displayed in bold and no user B process are launched. The session of user B has been unexpectedly closed!

Environment:
I have Jaunty 64bit (latest updates as of 20h00 UTC 2nd April) and user A has "Extra" visual effect activated.
NOTE: this user switch and back was working from Alpha 4 to Alpha 5, sometimes after Alpha 5 it stopped working, but as I do not use this feature everyday I cannot tell. I did not report it earlier out of laziness, sorry!
NOTE2: I have tested in a virtual machine (without 3D activated) and a 32 bit release of Jaunty, and I cannot reproduce the bug there. This is maybe due to the 64bit system or the 3D desktop effects...

Note: if this is the wrong identified package, please could you point me to the right one?

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
Package: fast-user-switch-applet 2.24.0-0ubuntu10
ProcEnviron:
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: fast-user-switch-applet
Uname: Linux 2.6.28-11-generic x86_64

[Huygens (huygens-25)]

I have done another test with user B first (which does not have any visual effect activated), switch to user A, and back to user B. I got again a black screen but by pressing the Magic Sysrq and K I got a login window (a plain GTK window without the Ubuntu look-and-feel) for user B. User A has no process active and sadly when I try to select user A again or simply logout of user B session nothing happen (I see the logout confirmation dialog, I click on logout, I am still loged in!).

[Phillip Susi (psusi)]

This package has been removed from Ubuntu. Closing all related bugs.