Not sure how well you know how to set speakers up, so i'll assume the worst and take it from there..
On your TV menu, check your connections, sound and speaker type. Make sure you've chosen the correct speakers in the menu and also have them at the correct levels.
Secondly, check the switches underneath the BL6000's and at the back of the 8000's. Make sure they are switched to left and right. You get a pretty bad hum when they are accidentally switched to 'Line'.. It's easily done. Finally, if you've had the carpets up - check you haven't knocked a spike from a gripper-rod through a cable. One broken wire inside a powerlink cable can cause all kinds of annoyances!
If you have the menu on the TV correct, the cables are good, and also the switches on the speakers are correct - it's almost certainly your dolby board. That said, in all my time dealing with B&O i've only replaced ONE dolby board. The other hundreds of times it's been one of the other items i've mentioned.
Good luck
Lee
BeoWorld - Everything Bang & Olufsen