DB1:Loading

Hello

Perhaps somebody has a hint on what I am doing wrong. I cannot get both MCDUs (CPT and FO) to load the navigation databases. I tried thousand ways, using navigation data from NavDataPro and Navigraph, but no matter what I do, both MCDUs just keep showing the text "DB1:LOADING" and "DB2_LOADING" below the "LOADING NAV DATA BASE" title.
It was working before, I am not sure if it stopped working after the update to version B45.4 or after trying to update the navigation database. Is there a description of the steps required to update the nav database and of the correct location of the navigation data files?

Thanks a lot in advance
Andre