With the introduction of non-domain member protection in DPM 2010, there seems to be some confusion using the SetDpmServer.exe. Over at the Ctrl-P blog, they posted clarification on the correct syntax.
http://blogs.technet.com/dpm/archive/2010/03/02/setdpmserver-common-syntax-mistake.aspx
Basically you can use either:
(A) the [-updatepassword] with the [-isNonDomainServer] parameters together
-or-
(B) the combination [-isNonDomainServer] and [-userName <userName> [-productionServerDnsSuffix <DnsSuffix>]]
-BUT-
Not (A) and (B) at the same time.
Hopefully that...
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