Custom Pipeline Component Adding Rootnode and NameSpace

Hi Gurus,

                 I am Sending message to the client using HTTP Post and using request-response Solicit HTTP Adaptor, When I send Request Message to the client If everything works fine Client Sends me Response Back to us and BizTalk is picking it up, The problem is if anything goes wrong like Request Message Not valid or Authentication Fails then Client is sending XML message <? xml….><Error>Error Message</Error>

Which does not pertain to my Respose schema hence its Failing,

Does anybody came across this scenario?

Possible solutions what I am thinking is 

1)Writing custom pipeline compoent at receive side which can add nameSpace and Rootnode to the Incoming message  So that BizTalk can Pick it up.

2)Bounding Receiving XML Message as XmlDocument So that BizTalk Will pick that message without validating it.

Is there any other approach  you guys can think of?

Thanks

BABA