Nocturnal paralysis is a well documented condition, if rare.
You may find the link below of use;
http://www.medlink.com/medlinkcontent.asp
I think it is regarded as a normal, natural phenomenon for the body to be paralysed whilst sleeping - this to prevent accidents through rolling out of bed, etc. Nocturnal paralysis, often accompanied by anxiety, happens when people wake but the paralysis persists.
Another possibly useful link for you;
http://serendip.brynm...du/exchange/node/1740