The message is Error code 335544721 Unable to complete network
request to host xxxxxx. Failed to establish a connection. No
connection could be made because the target machine actively refused
it.

I copied a program update to a number of users on a particular site,
and in all cases except, for one PC where this error message
appeared, the update worked. All of these PC's connect to the same
server. The update has also been installed on three other sites, with
no problems. The FB database on the server is obviously working, as
the other PC's were able to connect and the firewall on the server
was obviously allowing the connection. Now comes the peculiar part.
If, on the PC that is causing the problem, I re-install the old
version of the program, the error message does not appear and the
program works normally. I have re-installed the FB client on this PC,
checked the services file and windows firewall, and tried connecting
with the firewall turned off. In all cases, the original version of
the program connects, whilst the updated version produces the error
message. I have also tried connecting to a database on another server
to which this site has access, with the same results. This particular
PC is an older, slower PC with windows XP home SP2, whereas the other
PC are all newer with either XP professional SP2 or Vista. Other than
this, the setup is identical on all of the PC's. Can anybody help
please?