400 Bad Request on IS 8.2 webservices

Hi Folks,
I am incessantly getting http 400 - bad request message from a webservice descriptor that is trying to post to a webservice. I am not doing mascarading on the URL,etc , and the service is working fine from Soap Ui.(That is , it is returning the reponse fine) Am I doing something wrong?

Any inputs appreciated.

Please check with the network on both sides if there any firewall issues from your wM environment and remote site (external) as well…

Also is the WS ACL set to Anonymous or some thing else can you check?