RM 5.2.4 - Mixed 2003-2008 environment

We are upgrading servers to 2008 R2 (from 2003). One of the replication jobs I have running is  to mount a nightly snap for backup purposes.

The job was running fine in the all 2003 arena. Last night we installed the first (and most critical) 2008 R2 server.

When the job ran, it failed - the snap was created, but failed to mount on the 2003 server. Looking at the job properties in RM server, the 2003 Mount Host is no longer available. I only see the 2008 R2 server.

All servers are at the same RM level.  The 2003 servers have SE 7.1.0, and the 2008 server is SE 7.11.26.

I would like to know if this is a straight incompatibility issue between 2003-2008, or if I just need to update my 2003 server SE, Vavi Agent, Navi Client, etc.

Any thoughts or help are appreciated!