I was out of town on business for three days.  When I returned to work, I
noticed SETI was not running on my work computer.  I tried to start it
manually and got an "unknown error 100" message and SETI ended.

I restarted the computer and got the same thing.  I uninstalled and
re-installed SETI and still get the message.  Obviously I made no changes to
the computer while out of town.  The error occurs while trying to connect to
the server.

Computer:
AMD CPU running approximately 2 Gz.
Windows 2000 with all latest service packs and security patches.
Using Network Address Translation to connect to the Internet.
There is no firewall as such besides the NAT server.
Latest McAfee virus scanner, updated 3 days a week indicates no viruses.
Spybot Search and Destroy says no spyware or adware is present.

SETI has run perfectly on this machine for months.  I just see no reason for
it to suddenly stop functioning.  And ideas would be appreciated.