I'm getting absolutely no audio from my macbook pro, not even the startup sound.

It started when I was plugging a synthesiser into the computer's input via a 'monster cable'.
I got a mild crackling sound but nothing too unusual.
The Synthesiser made no noise when I played it.
I then restarted the computer and checked 'System Preferences - sound' and there were devices missing.
All I have now are the Soundflower (2 and 16 ch) devices in both the output and input sections.
When I click on F3, F4 or F5 all I get is the small volume screen with the 'no parking' sign on and an inability to change volume.
Also when I start garageband I get this message. Selected Driver Not Found. (-10202)

I don't think the problem has anything to do with the switch inside the headphone jack because there is no red light coming from it.

Is anyone else experiencing a similar problem or does anyone know of a fix?
Thank you for you time