HI Roberto,
I think this time your issue is the same I faced when I was installing same system. Check out my blog here: SAP NetWeaver Application Server ABAP 7.02 SP11... | SCN
What I did to resolve this was that I added into the file:
x:\usr\sap\NWG\SYS\profile\DEFAULT.PFL
following line in here:
dbms_type = ada
Means system was not able to recognize DB type. Adding DB type in that file should help.
cheers
m./