Do you have the Radio control set to AUX?
Not sure, I'll have to check

So, if I put it on AUX I cannot listen to the radio on the bike, but will be able to use the CB along with the MP3 in the Zummo or the XM along with voice navigation?
I don't have a ZUMO 550 but.....
You can't listen to the factory radio on AUX.
Push the power control button until you see AUX to access the ZUMO.
If you want the CB on push it again until you see AUX and CB on your display screen. Your CB, MP3 in the ZUMO, XM and voice navigation should work.
My set up uses a splitter cable under the right side cover like yours. One cable goes to my IPOD and the other to a Garmin Streetpilot 2720 GPS. I have to switched to AUX to access the IPOD or voice commands in the GPS. My voice commands only work when the IPOD is switched off.
I was getting some static from the GPS through the speakers and solved that problem with a noise suppressor. I plugged it in at the Y connector leading to the GPS.
http://www.crutchfield.com/p_127SNI135/PAC-SNI-1-3-5-Noise-Filter.html?tp=2653