No changes that we have made have made a difference. THe perceived fix to one site didn't turn out as expected. After researching it Riverbed actually has some fixes to F5 connectivity in recent firmware updates (6.1.5) however we are on an older version which requires some extensive updates to our Riverbed infrastructure. The other issue found was that Riverbed wasn't handling the encrypted RPC traffic properly. Exchange 2003 didn't have encryption on by default but 2010 does so Riverbed does something with the packets to cause a reset of the TCP connection. We have yet to schedule enabling encryption so don't know if that will fix it or the firmware update.
For now to solve our issue we've put a rule on the Riverbed to ignore traffic to/from the F5 VIP for Outlook.
Nimbostratus