Windows 7 - Headphones Not Working

Hello all,
I've recently build a new PC (Ultimate 64x) and am having troubles with the audio.
(oh and I have a ASUS P8Z68-V LX mobo)
Right after I installed Windows, I installed all the drivers including audio (which is the Realtek HD Audio Manager)
I plugged in the headphones by audio jack and they were working fine, until the next day when I unplugged them. The headphones didn't produce any sound, so I tried everything in my book to try and fix the issue (ie: re-installing drivers and deleting old drivers, fooling around with all the play back devices).
The sound "waves" under the volume mixer are moving, but no sound was present!
I even plugged the headphones into the right jack. This issue is very frustrating and I can't figure it out for the life of me. Please help.
G.M.

just a thought but have you tested the headphones on another device to rule out them being at fault. or even try another pair of headphones in the pc.

Yes, they work perfectly fine. I tried 2 pairs of headphones on the same jack and they still don't work.