No sound except via System Beep

I have just installed Feisty Fawn on a new Thinkpad T61. There is no sound *except* when the system beep sounds. In other words, if I am playing audio (CD, Realaudio, etc) I only hear the music when the System Beep also goes off. For example, if I do a Find in Firefox and hold down a character key, I can hear the music just fine. This happens with a fresh install of Feisty as well as after running updates and installing the most recent ALSA driver and support software.

I tried disabling the System Beep using "sudo modprobe -r pcspkr" after which there was no sound at all.

I am assuming that the fact that the desired audio does come through with the System Beep indicates that this is not a sound card problem.

I have gone through the Ubuntu Community Sound Troubleshooting and Debugging Sound Problems pages without finding a solution.

The problem has nothing to do with the computer waking from sleep (I have seen discussion of a bug involving that): it happens after a full startup.

Here's the configuration:

Thinkpad T61, 4gb RAM, 2.0ghz Intel Centrino Duo.
Sound card:
Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 03)