I am having the exact same problem, installed ubuntu 2 days ago and last night I noticed that the sound that it makes when entering a folder was getting a little weird, like it was coming in double and with bad quality, everything else was fine (Videos, Winamp, Youtube). I also installed service pack 1 last night and the sound was working fine except for the click thing already mentioned.
Today in the morning I woke up and started my PC and there was no sound.
Windows says there's nothing wrong with my drivers
or sound card, the file runs and says its playing but no sound comes out.
-Checked all the settings and tried different ones with no success;
-Re installed my drivers while on service pack 1, different drivers and also the same ones that used to work, no success;
-Disabled my Sound Card for a certain amount of time, no success.
-Uninstalled Service Pack 1 and did it all again, no success.
I don't know if this problem was solved i do wish it was cause i don't like the idea of waiting a year or more to get my sound to work. So someone please help me, pretty please.
PS: On Linux it is still working without any problem, so it's no cable or hardware problem.