I've had trouble getting the sound to work in Ubuntu 12.04 I'm running an Acer Aspire 5739g laptop. This is using a clean install. This wasn't a problem when ubuntu first installed. Rather, it was when I ran the updates that it stopped working. I already tried the suggestions on the ubuntu sites and other similar queries, and they haven't fixed it. Something in the updates is making my sound not work.

Edit: It turns out that this might be a bug (the sound issue, first paragraph). After reinstall, it happened again (it's not caused by updates at all, or any software, because I fixed it now w/o reinstall). It seems like I replicated it as follows: I changed auto-hide in the behavior tab of Appearance settings by turning it on, and setting the sensitivity to below the recommended setting. Then instead of restarting, I just logged out and back in. The sound stopped working again. I set the behavior settings to default, restarted, and now it's back to normal. Not sure if it's due to only logging out (and not restarting) or b/c I set my sensitivity to a low setting. Not sure if this helps anyone, but thought I'd mention it.