user cannot access email

[Bob Wooden]

This AM, I was home and decided to see if my server needed any updates.  
Not thinking that anyone was at work, yet.  When I arrived at work, it 
was discovered that one user was at work and signed into his client 
using Thunderbird.  The server was hung (when I got to work) and I could 
not get into it from ssh, nor a terminal, nor direct access to the 
keyboard and monitor attached to the server.  Upon reset, all worked, 
except that that particular user can no longer access Thunderbird.  An 
error box pops up indicating that "Thunderbird is already running, but 
is not responding. To open a new window, you must first close the 
existing Thunderbird process, or restart your system."  And included is 
an "OK" button.

System restart yields the same pop-up box complaint.  And I cannot find 
any running Thunderbird processes.  Further, other users can open 
Thunderbird, just not this specific user that happened to be online at 
the time of my command line update and upgrade.

Any suggestions regarding what to do now?