Sound problem with the P5E Deluxe

So i bought the P5E Deluxe motherboard, but im having som problems with the sound (Supreme FXll)

1: when i plug my headset into the green plug it detects a new unit and ask me what's plugged in.
I answer a headset from the dropdown menu. But it then says its not connected right and that i have to unplug and plug in again. But same error again. However, if i chose speakers in the menu instead of headset it comes up jst fine.

Any ideas?

2: When i select the "speakers" option sound works fine. Except!: I get this very low sound in the headset, kindda like a pc-speaker melody. The sound is really low, but its jst high enough to notice, so its driving me crazy when dont have any other sounds playing.

What can this be? Static or interference from other units?

3: I can't turn the volume to zero on the headset. Meaning that when i turn the volume wheel to zero theres still sound playing.

Could this relate to the problems mentioned above?

Any suggestions would be most welcome, as im very lost on this subject at cant seem to find anyone having the same problem on the net.