Left speaker gets no sound but both earphones do

["Jordi Gutiérrez Hermoso" <jordigh@gmail.com>]

I'm using an Inspiron 1420 laptop. The sound is an Intel chipset. lspci says:

     00:1b.0 Audio device: Intel Corporation 82801H (ICH8 Family) HD Audio
     Controller (rev 02)

A while ago, perhaps during an upgrade, perhaps during a physical
accident, I lost sound on my left speaker. This had happened before
when for mysterious reason I managed to mute the left channel only.
This time, though, I looked around in alsamixer, and it doesn't look
like the left channel is muted. Furthermore, if I plug in the
headphones, I do get sound in both channels.

Is anyone else experiencing something similar? Please tell me that
this isn't a hardware problem. :-(

- Jordi G. H.