I am also experiencing this problem with a HP Pavilion dv2120ca. I dual boot Windows XP and Ubuntu 7.04 x64. Sound does not work on first boot after using Windows. I have to reboot again (Into Ubuntu) without the power cable for the sound to come back. Sound DOES work on successive reboots (with the power cable), as long as I do not boot into Windows, in which case I have to follow the same procedure to get sound back.
I am also experiencing this problem with a HP Pavilion dv2120ca. I dual boot Windows XP and Ubuntu 7.04 x64. Sound does not work on first boot after using Windows. I have to reboot again (Into Ubuntu) without the power cable for the sound to come back. Sound DOES work on successive reboots (with the power cable), as long as I do not boot into Windows, in which case I have to follow the same procedure to get sound back.