Yes, I have the same prob. I have the same set up. I use an iPhone 4s, and use it for sending/receiving telephone calls and streaming music via bluetooth. The pairing did work for a month or so, now the iDA-X305s/KCE-400BT will not even pair with my iPhone. It tries to pair, but comes up with 'no unit' or something like that after the pairing procedure times out.
If you find a solution (firmware update or other fix) then please post it.
Thankx,
Greg