Gnome does not shut down nor log out user

[AG <computing account googlemail com>]

Hello

Using Gnome 2.30.2 on Debian testing:

When I try to log out of Gnome or shutdown the system using the "System" 
menu options, nothing happens.  I have to call up a terminal window and 
manually reboot the system.  Gnome is used in conjunction with GDM, and 
I don't know which is causing the problem.

My system is up-to-date and despite searching on-line I cannot find any 
information on either the cause nor the solution, altho' clearly a fair 
number of Gnome users seem to be experiencing this as an issue.

Any help for this please?  It is getting so frustrating that I am 
seriously considering switching to another DM.

Thanks for any input.

AG