I recommended checking the install disk because I have had similar problems in the past in which I went all of the way down to the source code to find the cause before going to the BDFL of Slackware for help, he was quick to recommend checking the install disk which in both cases were the cause of my issues.
As for your issue with the sound, if may just be a fault with pulse-audio. Pulse audio has been in beta for a long time and was finally released as stable on 9-27-11, so it is likely that the installed version is a beta that did not fit the expectations of the true developers.
However since the latest ubuntu is being released, it should have the updated version of pulse and other necessary application, so it might be a good idea to try it out. Just make sure to check the md5sum of the downloaded ISO and verify the disk when you burn it to make sure there is no corruption.