Inbound mail stuck in queue between Exchange 2003 server and Exchange 2007 server

Environment:
W2k3 sp2 domain,
1 Exch 07 server with HT,CA,
2 Exch 07 server with MAILBOX - SCC
1 Exch 03 server

Problem:
Mails from exch 03 moves outbound-inbound to the Internet perfectly but not to the exch 2007
And the mails from exch 07 outbound to the internet and to exch 03 perfectly, but mail from the exch 03 or Internet is stuck and accumulating in queues on the Exch 03 server.

Connectors all appear fine but no inward flow from Exch 03 to Exch 07. The 07 Mail Flow troubleshooter tool, when run against the 03 server confirms this, when run against the 07 server finds no problems.

MORE RELEVANT INFO JUST LOCATED:
Event Type:      Warning
Event Source:      MSExchange ADAccess
Event Category:      Validation
Event ID:      2159
Date:            17/01/2008
Time:            10:53:27 a.m.
User:            N/A
Computer:      exch2007
Description:
Process edgetransport.exe (PID=2520). Configuration object CN=exch2003-exch2007,CN=Connections,CN=First Routing Group,CN=Routing Groups,CN=First Administrative Group,CN=Administrative Groups,CN=COMPANY,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=company,DC=com read from adsrv.company.com failed validation and will be excluded from the result set. Set event logging level for Validation category to Maximum to get additional events about each failure.  

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
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