Exchange 2007 to 2010 Free/Busy not working and Autodiscover problem

I have recently installed Exchange 2010 into our organisation.  The existing install is Exchange 2007.  My 2010 config is as follows:-
I have installed 2 Hub / CAS servers and used Windows load balancing to distribute connections.  
I have 2 mailbox servers with a DAG.
Mail flow works perfectly (after some head scratching).
I created a couple of 2010 users for test.
I can connect via OWA and connect through Outlook if I manually configure the settings.
I can't connect via Outlook if i use autodiscover - it prompts for the user's password and tries to connect to a mailbox server, but the credentials are never accepted.  I have set the rpcclientaccessserver setting for all mailboxes to the correct CAS servers (not the load balance name).
Also when I look from a 2010 mailbox at a 2007 mailbox's calendar I can see the availability of the user, however when I look from a 2007 account I can't see a 2010 user's calendar - it says Free/Busy information not available.

Any ideas would be gratefully accepted.
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Madan SharmaConsultantCommented:
For free/busy to work Exchange 2007 to Exchange 2010 coexistence, you must set the webservices url on Exchange 2007 CAS servers to

check this link:-

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SaakarSenior Technical ConsultantCommented:
Check this link,
When you do a test email autoconfiguration for a Exchange 2010 user through Outlook where are URL pointing too? are they pointing to Exchange 2007 or Exchange 2010, they should show the URL's of Exchange 2010 now.
Alos make sure that IIS Authentication is set as per referred here...
GTC-UKAuthor Commented:
Excellent, this worked for me, thanks
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