[MAP911]

i was wondering if anyone can help me out. I have the newest versions of pandora and the newest version of telenav installed on my blackberry tour (which has os 5.0). When i connect the phone to to my car stereo system with an aux cable and run pandora and telenav at the same time, the phone ceases to recognize that there is a aux cable plugged into the phone and the audio starts to come out of the phone speaker. However when i use pandora with sprint navigation i do not have this issue. I was wondering if anyone could help me out? (i've already uninstalled telenav and pandora and reinstalled them both, in addition i reinstalled os 5.0, however i am still having the same issue...) i know its not the aux cable because it works fine with my ipod and i am pretty certain that the headphone jack on my phone works fine because the audio works perfectly when just having pandora open or having pandora open with sprint navigation.
i'd really appreciate any help that anyone could provide me,
thanks,