Looked at their KB, sadly nothing useful
I had this problem before on my first Toshiba laptop. I thought it was going to be a much larger problem than it really was. After a quick Google search, I was able to fix the issue. It was years and years ago but I think I remember it being related to the headphone jack. Some option was ticked that shouldn't have been.
I did do some googling first, but everything I found was related to accidentally disabling sound with the function key (something I checked and eliminated)
So it doesn't work with headphones either? Have you tried a live linux distro to see if it acts the same?
Not yet, it was running Windows 7 when the problem developed, I wiped and installed Windows 8 and it didn't help, I'll try the Linux option as soon as I have the time and report back on my results
How savvy are you in terms of taking the laptop apart?
I could very well be wrong, but maybe there's something broken, or a short in the headphone jack socket.
(although a long shot, I had to remove some debris from an old walkman I used to have that just went dead as far as sound was concerned, turned out that a piece of the contact had bent and was making a short circuit, I straightened it out, using tweezers if I remember correctly, and the walkman was fine again)
I've already stripped it down and here's what I found:
The machine's fan and vent were caked with dust, but I cleaned it out with a brush. Whilst it did substantially reduce the level of heat the laptop produced, I checked the motherboard and case and could see no sign of warping or heat damage. I could see no obvious damage to any of the sockets, and all the wiring seemed also to be largely intact but I didn't check for short circuits, I will have a look at that when I have the time.