I'm recently having a problem in my Lubuntu deskptop: sound through the speakers doesn't seem to work. The funny thing is: it works when I plug in my earphones. I've tried to unmute everything with pavucontrol and alsamixer, but everything seems to be OK.

$ sudo aplay -l
**** Liste der Hardware-Geräte (PLAYBACK) ****
Karte 0: Intel [HDA Intel], Gerät 0: HDA Generic [HDA Generic]
  Sub-Geräte: 0/1
  Sub-Gerät #0: subdevice #0

$ lspci -v | grep -A7 -i "audio"
00:1b.0 Audio device: Intel Corporation NM10/ICH7 Family High Definition Audio Controller (rev 02)
    Subsystem: Acer Incorporated [ALI] Device 034a
    Flags: bus master, fast devsel, latency 0, IRQ 44
    Memory at 58200000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd-hda-intel

Can anyone guess what's happening? It has worked until recently and it definitely works in my Windows partition.