Have You found the solution?
I have the same problem with XFI Surround 5.1 Pro, but it doesnt works with DDL wit any game...
If i disable DDL it works fine with option DD Music or DD Movie (Logitech Z680 - they work optical just perfect with PS3).
But when DDL is on, it works only with 2 front speakers.
Also what i have found, 5.1 DDL test works with Windows test but doesnt with Creative Console 5.1 test (?!).
At the end: DDL doesnt works at all...