The general problem with the Ubuntu graphical frontend is that it's the absolute end of the chain. If everything up to it is working, then it works fine. If any link upstream is broken, then it's useless.
In the case of sound, the general chain goes as follows:
kernel->pci or usb bus->udev rules -> alsa or pulse -> ubuntu config and application
Anything along that chain could be busted. My bet, pulse and alsa are fighting, which is usually the case. Alsa is a direct link into your sound card and will accept mathematical wave functions as input and output sound. Pulseaudio or Jackd is a digital mixer, so it takes all the applications that wants sound, mixes them together, and then sends the final waveform up the chain. Check these programs and use those names to start your troubleshooting/debugging search.
If you want the easy way to do things, try using the internal "dpkg-reconfigure" to just reinstall pulse, or jack, or alsa, or whatever is giving you trouble--kinda hard to know which from a "sound is not working" statement alone.
As for the scanner, that's almost guaranteed to be a udev problem, it's chain looks about like: