"NAV Customer to CRM 2011 Account - Failed to Read Entity Keys in Microsoft Dynamics NAV"

I have used the connector to integrate NAV 2009 R2 with CRM 2011. All entities are integrating as expected except the account entity from NAV to CRM. The reverse works. Whenever I try to integrate Customers in NAV to Accounts, I get the error "Failed to Read entity Keys in Microsoft Dynamics NAV". Fiddler2 does not give any useful information. What step could I have missed, I've applied the hot fixes and followed the connector setup sequence.