key shortcut not working

[Thomas Blasejewicz]

 Good evening
I am using Ubuntu 10.04 (English version).
After I initially installed it, I at some time created a few keyboard
shortcuts,
including
Win + T for Thunderbird
Win + F for Firefox.

They were working.
Now, I have not been using the Linux machine for some time and in
between there were 2-3 updates,
Win + T for Thunderbird does "not work" any longer. I mean, it does -
somehow - start Thunderbird,
but every time I do that, I get the following error messge:
"Thunderbird is already running, but not responding. To open a new
window, you must first close the existing Thunderbird process, or
restart your system."
There is no other Thunderbird process and restarting the system does not
change anything.
If I change the KB shortcut to let's say Crtl+Alt+B, it works without
any errors.

This is not really important, but I would still like to know what is
going on.
Thank you.