sound in KDE doesn't work anymore, AC-3 does work though

[Sander van Loon]

Ok, something very weird happened. Let's begin with my hardware, I have a 
Soundblaster Audigy Player soundcard and a Creative Desktop Theatre DTT 2500 
Digital 5.1 speakerset. After I installed Kubuntu a month or so ago, all I 
had to do was unmute the "Audigy Digital/Analog Output Jack" switch in KMix 
(because in every Linux distro I've ever used it was muted by default, but is 
done intentionally by ALSA I heard) and then the sound would work. And it has 
been working ever since I installed Kubuntu, until yesterday.

I was watching a video file with AC-3 sound in Kaffeine. After that I opened 
another video file without AC-3. But I didn't hear sound anymore. I opened 
amaroK to check if it was Kaffeine-specific, but amaroK gave me no sound 
either. I started a game, Enemy Territory, but sound didn't work there 
either. I rebooted to Windows XP and I noticed that the sound was working 
fine in Windows XP, so it isn't my hardware. I rebooted to Kubuntu again, but 
still the sound didn't work, except when I opened a video file with AC-3 
again, then I would get sound.

I checked everything in the mixer, but I didn't notice any abnormalities, 
nothing is muted... very weird, and I have no idea what to do. Can anyone 
help me with this? If not, can anyone tell me how to "reset" the sound system 
and it's configuration files, maybe it will return to normal then?