Hi Michael,
This is bonkers!!!
From what I can tell that message is caused by a missing or invalid key that is created during the set-up routine and with Opus is stored in the Registration node under Local Machine / Digital Workshop.
It's seems unique to the actual set-up and even re - imaging a drive invalidates it and thus there is no apparent way around this. If it doesn't create it during the install - it simply won't run.
My first guess would have been that this is a 64bit issue but Opus works where Creator fails. If I owned Creator I could probably run a registry trace and work out what was failing but using the evaluation edition this is not possible - sorry
You could check that the Registration key is the problem - I think it will be under
Local Machine\
Software\
sysWOW64\
Digital Workshop\
Registration\
You should see a DWORD entry. If you have a sub-node called evaluation - I think this is for the demo version of Creator.
Mack