I had installed Linux Mint 13 on a separate partition and mounted my shared /home, and was using dave2 so I didn't overwrite my default user's Workstation 8 settings.
(I remember seeing this on the forums before -- it's a group-membership issue on Linux.)
Long story short, dave2 was not a member of the proper groups to have sound.
' id dave ' # find out which groups I'm in
' usermod -G adm,cdrom,sudo,dip,plugdev dave2 ' -- logout of X and log back in, and Bob's yer uncle.