Organization not detected when running E2010 SP3 setup

I am working on an Exchange 2010 organization with two multi-role servers in it. They are running SP2 with no rollups. I attempted to install an additional server using SP3 media, but during the setup, it does not detect the existing Exchange organization, but instead asks me if i want to create the First Organization object.

Initially I thought that perhaps this might be because some schema needed updating, so I ran setup /PrepareDomain using the SP3 media, but when I reran GUI setup, I got the same thing: it doesn't see an existing Exchange org and wants to create one called First Organization.

I used ADSIEdit to confirm that the Exchange org objects were there, but I'm not sure what to look at next.

Any ideas?

Dave Shackelford