VF02 - Error in Outbound Idoc - "Form of Address Key is not defined"

Hi,

While processing the outbound idoc in VF02, i am getting an error "Form of Address Key is not defined".

Our system has been recently patched.

While processing the idocs in VF02 (for the invoices created earlier to the patching date), there is no error & the Idoc gets created.

I am not sure why i am gettting the above error now (that is after patching).

Please let me know if i am missing something here / is it because of the patching.

thanks & regards

Narain