No sound through headphones, speakers working

I have an ACER 5570 notebook with Vista. Up until yesterday my headphones
worked fine. Now when I plug them in I hear nothing. Notes-

-An information box pops up and says a jack has been plugged in.
-There is only one place in the computer for the headphones to plug into,
and it says SPDIF next to it.
-The Speakers still work when the headphones are unplugged.
-There is no external control on the computer for volume.
-The headphones are in working order.
-The driver is RealTek high definition audio. It is up to date.
-Ive tried restarting. No luck.

Id love it if anyone could help me, or at least point me in the right
direction.

There is a setting to output two different audio streams to front and rear
sound outputs.
RealTeck, speakers tab, note upper right corner link for advanced settings.

Thanks for your reply Mark, but I had no luck. The advanced settings link
only has options for Recording Device / input.
Have played around with the other settings on the page too, but still
nothing :(

Hi
I had the exact same problem with my Acer 3680. Internal sound working
fine but no sound from headphones etc and the frustrating part was that
it kept saying audio devices working fine.. Now this might sound weird
but.......I took to it with the vacume cleaner (you know I put the
vacuum to the jack where the headphone plugs in and wallah!!! it worked.
I don't know maybe or obviously it just had a bit of dust or dirt or
something in there. Worth a try!!!

The same thing happen to me I also have an Acer on vista. But I need this
thing to work right now. My speakers do work, i went in the driver and did
the test. I heard sound but that was the only sound i heard. o matter where
I go on line or media player, there is no sound. I read somewhere that some
of the virus protecting programs have gliches that can cause no sound on
pc... Im going to take this thing back in the morning.