I can't, for the life of me, figure this one out. I have a 2 1/2 year old Gateway PC, which I just upgraded the RAM on. First I went from 1GB to 2GB, which was fine. Then, a few weeks later, I upped again to 4GB. This is when I lost my sound.
Everything else worked fine, but my PC went mute. I found that it was fine when I used the front headphone jack, but the rear speaker output was a no-go. And to make things even more confusing, the rear line-in jack suddenly changed itself into the speaker out, and the mic ports stopped working completely! I checked the sound settings, and even the device listings were different.
When I took the newer 2 GB out, it was fine again. I thought maybe this was a Vista problem, and I was getting fed up with Vista anyway, so I blasted it and installed Ubuntu 9.04. I found I had the same exact problem with the sound, so I know it's a hardware problem, not software. Also, I took turns with the two RAM modules, just to see if one was faulty, but they both worked fine on their own. They just don't play nice in the sandbox!
Has anyone else come across this? I've Googled the hell out of it, with no results.