Tried using the black pages and see if the same problem exists there? if it does it looks like N3V are going to have to reset it at their end.
As a matter of interest are the daily updates up to date or has that stuck as well?
Another thing to try maybe is in Content manager > Settings > Internet, change the connection from IE settings to No proxy server if on IE or the other way round if on No proxy, then close CM, reboot and then restart it, I seem to remember that kickstarting things before I got an FCT.
Long shot but were there any Windows updates around the time it stopped working properly? I did have a case once a couple of years back where an update reset the Windows firewall and blocked certain parts of Trainz.