shoping cart approv error seen in custom portal and not in standard portal

Hello,

There is a custom portal ' My Purchase' . when a shopping cart approval workitem is executed then there are errors like 'no address found for aprtner function type location' and enter no more than one partner of type location'

When the same workitem is executed from standard portal it works fine without any errors.

Could you please guide me with initial thoughts on this issue ? I am very new to portal and dont know how to proceed

thank you