I'm using Spotify on iPhone 4S (Verizon), iOS 6.0.1 and having issues with Siri while driving.

When I press and hold home button on my iPhone to launch Siri then it launches (looks like phone call from car perspective) as usual but after 2 seconds "phone call" ends. However, Siri icon doesn't disappear on iPhone's screen.

Result: no music, no Siri.

It doesn't occur without a car (works as expected - Siri listen, answer and after Home button music start playing).

While driving it doesn't matter is Spotify app in foreground or in background - still having issues with Siri in both cases.

I can normally use Siri with stock Music.app from iOS and also with third-party apps (tested with Downcast).

Car is Toyota Prius V 2012 model Two (Basic audio).