OK, that's strange.
As a test, is there any chance that you can setup a new Test Mailbox on the Exchange 2007, enable it in EV, archive some messages, and try the same restore?
I suspect the following:
- Error Code: 0x800706ba is usually "RPC Server not available"
- As restores to PST work, I suspect that EV wants to write a message into the remote Message queue from the Original Server, to command the "New" EV Server, where the archive is located, to restore the item into the user's mailbox
This could be because of blocked ports.
This Article backs this theory (same error code, other situation):
http://seer.entsupport.symantec.com/docs/290438.htm
I think you should concentrate on this:
http://seer.entsupport.symantec.com/docs/307238.htm
Especially Port 2105 RPC for MSMQ.
As a first test, could you disable Windows 2008's own Firewall for some minutes and try again?
If that does not work, I suggest you ask the Firewall Team if they could log the traffic, and see which ports are blocked and accessed during restore.
(If you have Firewall's between your EV Servers)
Hope that helps
Regards
Michel