have settings in firewall of leopard to accept all incoming connections but no luck now... port 55555 is always closed when it used to be open before i upgrade
From which version did you update from?
Also: eventhough Transmission's code hasn't been changed, could it be that the updated libraries did something?
I doubt it. Regardless, Transmission's port forwarding is handled by miniupnp (http://miniupnp.tuxfamily.org/), so that's probably the best place to direct your problems.