Which producer are you connecting to:- WebSphere 7.0 and WebSphere portal 6.1.
Is there any error message on the producer side that could indicate what's wrong :--No error messages at the App Server level
one of the newtwork guy at producer site says :root of the issue lies in the COOKIE and how it trying to keep the SESSION LAYER open
Also attached the screens shots of network trafic at producer site