I've read a couple of threads with people having similar issues, but nothing has helped, so I try creating an own one. Here goes:
First, sound has been working well earlier, this is something that changed recently. I have a Dell Latitude D830 with a docking station, and this weekend I decided to fix some trouble where Skype had a conflict with Rhythmbox and Flash applications while the computer was docked. I followed the steps in this guide: http://ubuntuforums.org/showthread.php?t=789578 (which I have used to solve this problem when the laptop is un-docked, but this did not help for the docked setup).
Since then, a screeching, high-pitched noise/beep at maximum volume comes out of my speakers, starting somewhere halfway through booting, and continuing indefinitely - until I plug something into the headphone jack to silence it (if I plug in headphones, the noise comes out of them instead). The noise is independent of mute, volume change, etc. If I play a sound, I still only hear the noise. I have tried to uninstall ALSA and pulseaudio, nothing helps. I have also gone through the Comprehensive Sound guides in this forum without success.
While tweaking around with the ALSA installation, I now also get an error message after logon, telling me that something is wrong with the certificate for bugtrack.alsa-project.org:443. This error, however, started after the noise error started.
I have no issues at all in Windows Vista (the computer is dual-boot), neiter in Ubuntu when the computer is in its docking station.
I am quite new to Ubuntu, so the more basic steps you include, the better (I know how to start the terminal, execute commands as root, but not much more than that.)