3GS with iOS 4.2.1 update - voicemail no longer working through bluetooth?

Question

Hi Folks.
I've been happily using my iPhone 3GS with my Jeep Patriot's bluetooth/stereo system for months (it's called a Mygig). However, I just upgraded to 4.2.1 and now when I connect to my voicemail the sound doesn't come through the system - the iPhone thinks it is sending the audio to the stereo, but the stereo remains idle. So I have to select one of the audio options (phone/speaker) to hear anything.
If however I make a phone call, or if the phone rings and I answer it, it works fine.
Even if I use voice dialling to call voicemail, that works through the bluetooth, but as soon as it has finished the voice dialling and actually calls voicemail the stereo goes back to being idle again, even though the phone thinks it's still connected.
So at present if I want to connect to my voicemail while driving I have to use the speaker. Only for voicemail. Weird!
I am thinking this is a software update issue, as it worked fine prior to the update, and everything other than calling voicemail works fine through bluetooth.
It's as if the phone isn't talking to the bluetooth properly when it's dialling the voicemail, which is somewhat of a 'hardwired' thing, given it has its own button. I tried tricking it by dialling the actual number instead of using the voicemail button, but the iphone knew it was voicemail...
Any ideas?
PC

Answer 1

Yah, have the same issues since upgrading to ios421. Pretty annoying... I have two cars, and the issue is same with both bluetooth systems. I am able to make and receive calls but cannot listen to my mobile voicemail.