Help: Sony Vaio FW on board speakers suddenly stopped working

Hi all, I'm hoping someone can help me brainstorm the problem I'm currently having with my Sony Vaio VGN-FW290. Current operating system is Vista 64.

The onboard speakers suddenly stopped outputting sound in the middle of a video call. I wasn't doing anything in particular when the sound cut out. I can hear sound through standard headphones if they are plugged into the jack. Looking at my sound control center, my laptop is able to tell when the headphones are or not plugged into the jack, so it's not a detection issue where the computer thinks the headphones are always plugged in.

When I go into playback devices, I have a default Realtek High Definition Audio Speaker/HP device. It says it is working. If I click Test, the indicator levels move so I know it is trying to output sound, but nothing comes out of the onboard speakers. Plug in the headphones, click Test for the same device, and I can hear the sound through the headphones.

I have scoured all my sound options, updated the drivers, and tried a system restore, with no luck. It seems like maybe a hardware issue, but it seems odd that both speakers would physically fail at the exact same time. I'm not sure how may waystations there are between the seemingly working sound card/board and the problematic soundless speaker, either.

Can anyone think of anything else that could be the issue? Thanks very much in advance.