Port forwarding issues

[Desmo]

I have a network with a NAS running transmission, an iMAC, a WDTV Live and a few wireless devices (phones).
I have a couple of apps that require port forwarding to work and I subsequently have these forwarded to their requisite machines.
A few weeks ago, one of my programs wouldn't connect to the "list server" and I'm also getting transmission errors "Tracker not found". In the Transmission setup I have checked to see if the port is opened. It's stating that it's not.
Now I'm not an idiot, I know how to forward a port so I have deleted and reinstated these to no avail.
So I tried a new router, no dice, same issue.
I have put machines on the DMZ, bridged routers and done just about everything I can think of to get a port open (even though it says it is on the router), I can also see uPnP putting it's routing in the tables (when I turn it on) but still no dice.
Funny thing is, IM, Web traffic etc seems unaffected and it's platform independent, OSX, Linux and Windows all have the same issue.
Christ, I even put the Windows box on the DMZ without a firewall and it still wouldn't work.
Spoken to Telstrarse and they say they aren't blocking anything although we did get a new DSLAM fitted not so long ago after an outage of a few days.
I am utterly stumped.

[I Fancy Holidays]

I have a network with a NAS running transmission, an iMAC, a WDTV Live and a few wireless devices (phones).
I have a couple of apps that require port forwarding to work and I subsequently have these forwarded to their requisite machines.
A few weeks ago, one of my programs wouldn't connect to the "list server" and I'm also getting transmission errors "Tracker not found". In the Transmission setup I have checked to see if the port is opened. It's stating that it's not.
Now I'm not an idiot, I know how to forward a port so I have deleted and reinstated these to no avail.
So I tried a new router, no dice, same issue.
I have put machines on the DMZ, bridged routers and done just about everything I can think of to get a port open (even though it says it is on the router), I can also see uPnP putting it's routing in the tables (when I turn it on) but still no dice.
Funny thing is, IM, Web traffic etc seems unaffected and it's platform independent, OSX, Linux and Windows all have the same issue.
Christ, I even put the Windows box on the DMZ without a firewall and it still wouldn't work.
Spoken to Telstrarse and they say they aren't blocking anything although we did get a new DSLAM fitted not so long ago after an outage of a few days.
I am utterly stumped.

Have you tried doing some sort of tunneling to remove telstra from the equation?

[Desmo]

No I haven't.

[Captain Starfish]

Ensured that your inbound port works within the lan? Maybe shut down the host and get something simple listening on that port, then try to connect from another machine on the lan?

Once you know the box is OK (hey, could be firewall on the box or something silly like that) then move out to the next step. See if you can ssh to your router and telnet back to the port inside. Now see if you can do it via the NAT.