Ok, I have the same motherboard...
When u install the sound driver it by default installs that IDT (somnething like that i dont remember exactly) sound manager. Check on the jack panel if the software is recognising the jack as line in and not as microphone (i know theres a mic jack but that can happen)
If that is not the problem check whatever software u are using to record if it is using that jack as input.
PS: sorry about my HORRIBLE english spelling... is not my first language