At the time, libflashplugin-nonfree was version 9, so to get version 10 I had to install it myself from adobe.

I took a look at that thread. I don't think there's a relationship between those problems and my situation. flash videos consume 15% of one core on my machine in normal mode. Youtube works just fine in full screen mode. Hulu works fine in full scree mode at top quality. Until the sound fails. The sound worked fine on this box for 9 months without any issues before the problem started.

This machine is Intel Core 2 4300, 1.8 GHz. The video is NVidia GeForce 6200 LE using the debian free nv driver, not the NVidia "tainted" drivers.

Youtube videos and other flash sound work without this sound problem on my 500 MHz Pentium.

Alright. Let's try pulseaudio. Do this:

grep -i pulse /var/log/messages

after trying to run flash sound. Even if there is nothing, try uninstalling, then reinstalling pulse audio, and try flash in both circumstances.

Note that pulseaudio is not installed. I noticed that people have reported problems with pulse audio. But 'dpkg -l|grep pulse' reports only 'libpulse0' installed.

Since you've already got problems, give it a shot. Kind of running out of options here... A reinstall might be our only option, but I'd hate to see that.