Speaker feedback and XBOX (Dolby Dig) question

I have two questions, the first concerning speaker feedback of some sort and dolby digtal support for my xbox.

I left for spring break and when I came back to school my Klipsch 5.1 ultras were acting strange. Whenever they do not have an input signal they give a loud buzz sound until they get another signal. Prior to break they did not have this problem, for example I have the speakers volume set at 70 and I controled the output volume through a Creative DTS decoder, and this worked extremely well, with no "buzz noise" (even when it did not have an input signal). But now it's giving this noise even when i naviagate dvd menus, as I found out when watching DS9 seasons, when i click to go to a submenu it gives the "buzz noise" inbetween menu screens. This is a huge inconvience and any thoughts would be appricated.


Alright, second question. I bought an xbox with all the proper optical adapaters for true surrond sound and hooked them into my Creative DTS decoder. I recently bootlegged Brothers in Arms, and in the intro screen it says "Dolby Digital" supported. Although on my decoder it does not switch to the Dolby Digital mode like it does on movies that support the format. As of now i'm just using Dolby Pro Logic II is this just as good or is there something I'm missing to get the decoder to switch to Dolby Digital. Thanks Max.