Macbook Pro volume greyed out -- no internal speakers available

The volume on my macbook pro has suddenly become greyed out. I haven't installed any updates or made any modifications to the computer, it just suddenly became greyed out after waking the macbook up from sleeping.

I've tried resetting the PRAM, but I don't hear any chime at all when I start up my computer, no matter how long I wait/how many times the computer re-restarts itself.

There also seem to be no internal speakers detected when I go into system preferences. For both input and output the computer detects 0 devices.

Thanks so much in advance for any help!!

Try switching back to your internal speakers with [alt]-clicking on the speaker icon in menubar. Many interfaces don't support volume adjustment and thus the control becomes greyed out.

The switch in the headphone input could be stuck, you can put in a headphone jack and wiggle it around. Don't be afraid to use a little force, just don't break of the plug. I had this problem too and this solved it for me at least.