Additional information:
The client PCs I've been trying to use the app from are Windows 8 64bits (which also used the app with B1 8.82).
Now I tried on an old Vista 32bits, and it WORKS TOO.
Maybe the problem is related to the DI API 9.0 and mixing 32bits app/api with 64bits SQL Client on a 64bits WIndows 8? Somehow it works on the Windows Server 2008 R2 64bits though.
Joao