Hi Julio,
The problem is indeed solved , we contacted SAP Support ; it is a very recent bug, SAP development support provided us a single jar file , responsible for Java Administrator authentication. We copied the jar file, then resumed SUM patching and the Administrator was immediately able to connect.
The jar file was not contained in the latest SUM package (December 2014), I do not know if it has been updated now.
So , you may need to open a sap customer call, and insist, it is not a network or authentication issue.
Communication can be... hum ... tricky ... with some sap support consultants.
Good Luck !