Toshiba Satellite Sound quits

[Basil1x]

Up until about 2 weeks ago, everything was working properly. Now, the sound works for varying lengths of time, then quits. This issue only affects the internal speakers; if I am using the HDMI to play audio, it is unaffected. I have tried everything I know, up to and including a fresh install.

the particulars:
Ubuntu 12.10
Toshiba Satellite L755-S5167
Bluetooth Dongle (for external keyboard and mouse when using HDMI)
External WD MyBook 2TB USB HDD

The sound works under Win7. It also works under Knoppix LiveDVD. It does *not* work at all with Puppy Linux.

alsamixer claims the sound is working even after it quits.

Could this be something Windows 7 has done to my sound card? Some 'feature' I must turn off in Win7 so my sound will continue working?

Any help would be appreciated.

[Basil1x]

Thank you ever so for all your help. Given my experience, I'll not bother posting again.