I have a weird issue :(

I previously had a 2 WAN setup with incoming FTP traffic on the second WAN directed via a virtual server which hosted an FTP server with passive FTP etc all set up. This has been working fine for well over a year. Yesterday I added in a third WAN connection which did require MAC spoofing on the appropriate port and set up the routing so one machine in particular only used the new connection (in the same way that the FTP server machine specifically used the second WAN) 

This all seemed to be fine until I needed to access my FTP site externally and it simply failed to connect. I setup another FTP server on a separate machine and setup the router poet forwarding etc and tried to connect to that using the new WAN connection but once again there is no sign of the FTP request reaching the server - I have checked the windows firewall logs etc.

The weird thing is I have a similar setup for POP3/SMTP on a different server on the second WAN and that is still working just fine.It just seems that incoming connections on Port 21 have suddenly not been accepted.

Has anyone got any ideas, I need FTP working!