The "About This Mac" looks ok. It says Intel High Definition Audio, with underneath Headphone, Line Input, Speaker, Internal Microphone, External Microphone / iPhone Headset, S/PDIF Optical Digital Audio Output, S/PDIF Optical Digital Audio Input. Clicking on each one, nothing says missing or corrupted or whatever, it's all normal. Speaker says "Connection: Internal" and S/PDIF Optical Digital Audio Output says "Connection: Combination Output"
Under Sys Pref and Output it has "Digital Out" with type "Built-In Output" selected. But for "Settings for the selected device:" it says "The selected device has no output controls."
I'm running a MacBookPro, Model 5,2 (3.06 intel core 2 duo). Latest version of OS X (10.6.4).
I've tried plugging in headphones, and the volume controls come back then, but as soon as I unplug them it goes away. Tried the normal Disk Utility stuff and simply restarting it as well, but nothing worked.