I had my radio unit fixed by Santa Cruz HD after getting some advice from the HD Forum. The fix was replacing a chip in the radio itself, noisy CB radio transmissions were fixed. Matter-of fact there were 3 of us in the Santa Cruz HOG group that had bought 06 Ultras and all had the same problem. SCHD replaced the chip in all three radio units under warranty.
Also go to
http://www.harley-davidson.com/cp/moar/en/software.asp to get the software updates for the harmon kardon
As Tbradley posted: Have the Service department at your dealership contact Steve Simpson (Steve.Simpson@harley-davidson.com) inTech Services at Harley-Davidson Motor Company. Steve was very helpful in resolving my issues with the HK CB.
After SCHD replaced the chip, I was a happy camper and especially those who were listening to my noisy transmissions.
OneLunatic