[jtdoom]

Hi,
JackSense with AC97 front and HDaudio back.

what's that mean?
The BIOS can be set to either, and the Front audio connector has to match the BIOS choice.
The Back can do either, and there leis the cause of the problem.
AC97 has different wiring for JackSense, and the front, wired up to AC will offer its BIOS choice (HD), which will confuse the person making the choice.
When YOU force HD to AC, it is wrong, at times, but not all the time.

Lessons learned, Check BIOS before you connect 5.1 or 7.1 or 2.1 or straight 2 line stereo headphone (Zalman have a splendid 5.1 headphone, btw), because that is where the confusion begins.
Kind regards, Jaak