I had this problem a few years back with my HTC (which I still have and paired fine).

The problem is the way you are pairing it.

I cant remember exactly how I did but, but it wanted to auto pair/auto pick the type of pairing. I think I had to tell the phone first to find the X5 BT. By memory, I manually told the phone to look for devices, then put the X5 in pairing mode. When it found the device, I then told the phone what device it was (BT headset, not a handsfree device). This isnt Gospel, but gives you something to play with.

The only annoying thing I have is that the volume is too low (and the volume knob doesnt increase the volume either) and when you are driving along, you cant hear that well (like the auto increase in volume that happens with the radio, isnt working with the phone and I am sure it should). Adjusting volume on the phone doesnt work either as it is at max. I think somehow when it paired, it thought the BT volume of the car is on max already.. Havent bothered too much, but one day I will get around to looking into it.

Rob