Solved! Go to Solution.
... I have registered the new database all the ways possible, the web manager, Server Properties on Catalog, and double clicking the error. No matter what I do the same error comes up.
... The other thing is I have other databases in this SQL instance that are shared via ArcServer that are registered and working properly.
Thanks man!
It is a really strange behaviour. It´s still present in ArcGIS 10.3, so please ESRI read this and correct!, this problem was driving me crazy