I had the very same thing happen with the Nav-V paired to a RAZR Maxx HD and an Interphone F5XT.
This is what I did to resolve the problem, I'm not 100% sure which thing worked.
I took all 3 devices in the house and unpaired them and repaired everything from scratch, my F5XT has several functions (menu items) that you can toggle thru (Setup, Intercom, Music Streaming, FM, Phone etc) , your Sena does too, after all three devices are paired together put your Sena in Phone mode and try to make a call, my trio of gadgets worked just fine after that.
The other thing I did was to clear the cache on the RAZR.
Remove chocks and chains.