I'm not sure what I am doing wrong but the 'Audio Input Selection' keeps greying out. The only fix I have found is to reset the camera, which is not a long term solution, especially as it only seems to be temporary. I'm new to the camcorder format, but this really has me stumped.
Solved, just after posting... it seems that when the camera is in pre-record mode the 'Audio Input Selection' is greyed out for some reason. Huh.