Shuttle SD39P2 issue - Front headphone jack not working

[unborracho]

Has anyone had this issue? I just setup this shuttle SD39P2 system and when I plug my headphones into the front jack the sound still comes out of my speakers and nothing through the headphones... somewhat frustrating. The mic-jack in the front works just fine though... as do the USB ports.

I'm using Vista if it makes any difference.