My iphone 4 no longer plays music in my car via auxillary port

I was using an auxiliary cable to play music in my truck successfully for several weeks when it mysteriously stopped working. I drive a 08 Chevy Silverado equipped with an auxiliary jack. I have tried another Iphone4 of the same type with the same OS and it works without issue. I would normally listen to Pandora all day, so this has become a frustrating problem. Note-
- The phone plays music through it own speakers, our home stereo, and headphones w/o issue
- I have tried switching cables that also work with alternate phones of the same type and OS
- I have tried resetting my settings on the phone in question to no avail
- I am certain that the stereo has the 'auxiliary' option selected
- The volume is indeed turned up everywhere possible, itunes, the stereo itself, Pandora, the phone etc
- I have not recently updated the OS
- The phone played music from my list as well as Pandora and other listening venues perfectly for several weeks with no problems whatsoever

:confused:This problem is eating at me and I appreciate any info anyone might provide- Thanks!!

[iphone 4][car][speakers][truck][auxiliary][cable]