sound starts at login, then stops shortly after

My sound card worked fine until yesterday when I was pompted to run the Update Manager. After some libraries were updated, it stopped. When I initially login, my sound card is listed under Output in the Sound Preferences window. Then it inexplicably changes to "Dummy Output Stereo". This problem occurs with other accounts on the system. My sound card is a VIA VTI780-A. I'm running Ubuntu 10.04. When I type in aplay -l at a shell prompt, I get this output: **** List of PLAYBACK Hardware Devices **** card 0: VT82xx [HDA VIA VT82xx], device 0: ALC662 rev1 Analog [ALC662 rev1 Analog] Subdevices: 1/1 Subdevice #0: subdevice #0 card 0: VT82xx [HDA VIA VT82xx], device 1: ALC662 rev1 Digital [ALC662 rev1 Digital] Subdevices: 1/1 Subdevice #0: subdevice #0 Thanks.:confused:

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