I've read quite a few stories about singers who lost their singing voices when dealt with stressful situations like a divorce. Found this article while browsing the Net:
http://www.britishvoiceassociation.o...tion-voice.htm
When we perceive something as threatening or upsetting the body reacts rapidly, preparing for action and producing physical changes that we are all familiar with. These may include:
Increased muscle tension
Increased heart and breathing rates
Perceived changes in temperature with shivering or sweating
Tremor
Dry mouth and throat
Common physical signs of distress include:
Gut problems: (e.g. acid reflux and irritable bowel syndrome)
Skin problems: (e.g. eczema /psoriasis)
Back, neck or other muscle pain (including laryngeal pain)
Breathing difficulties: (e.g. over-breathing panic attacks, a trigger for attacks in some asthmatics)
Hoarseness (dysphonia) or complete voice loss/whisper (aphonia)
Well, some of you observed that Jon has breathing problems and drinks a lot on stage. That would fit some of the signs at least...