I refactored an existing database and discovered a constraint with a minus "-" in it's name. The tool we used before put quotes around this very constraint name and Oracle accepted it. ModelRight does not quote it, so creation fails.
I was not aware of the fact that Oracle would accept it and I renamed the constraint immediately so the problem is solved for me.
You might want to consider this in some future version though, since it's allowed by Oracle and others could have this problem too.
Regards, Peter