Adding 2008 DC to 2003 domain but replication not working

Hi all.
My aim is to promote a Windows 2008 member server to be a DC in a 2003 domain. It's important to know that this domain (Forest/Domain Funtional Level both Windows Server 2003) once had three domain controllers but now only has one (there were problems!) and so some months  ago I was forced to seize all of the FSMO roles. Nevertheless, the domain has been up and running (yes, there are a bunch of errors in the logs though, especially DNS, etc.).

Right now I'm stuck on not being able  to successfully run  "adprep  /forestprep". I am  receiving the following message:
"The schema master did not complete a replication cycle after the last reboot. The schema master must complete at least one replication cycle before the schema can be extended."

I'm certain that the dormant entries for the 'extinct' DCs in my AD is what is causing this problem but is there a way to force the schema update anyway? I can't find anything more about other possible switches to the 2008 adprep.exe command in order to do a 'forced' update, so I imagine I am forced to do a cleanup of my AD instead but am pretty certain that just deleting the objects for the no-longer-existing DCs will not be sufficient. I don't want to spend days on this (we're understaffed - but who isn't these days?) as it  is basically a test domain, yet on the other hand I don't want to blow it all away and start over from scratch because there are several 'test' machines running in it.

So, how can I clean up my AD and get this to work? Alternatively, could I just export most of my 2003 domain AD objects and then import them into a new 2008 forest that I create (better than starting from scratch)? What would be easier/faster?

Thanks for your help.
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If you haven't already done so, use the metadata cleanup function of ntdsutil to remove entries for the defunct DCs.  This doesn't take long and might allow the schema upgrade to continue.

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cfsaAuthor Commented:
Thanks, the metadata cleanup actually worked, though I would have liked to know about the object export and import into another domain.  
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