Hmmm.
Feeling something pressing on your chest in bed is a very common theme in ghost stories. It's also a symptom of petit-mal epilepsy. As are seeing flickering lights. Add a dodgy dream, a bit of imagination and you've got a scary ghost.
(robbersdog, Mon 27 Jul 2009, 12:32, 2 replies)

Thats very true
But there were many other things that couldnt be explained, cold spots, balls of light, objects moving etc.
(insomniac-surfer oh go on then, just this once, Mon 27 Jul 2009, 15:49, closed)

A mare.
Its where the word nightmare comes from, the mare being an evil spirit that sits on a sleepers chest causing paralysis. The true cause is the dive reflex, a natural mechanism that freezes the body during REM sleep so we don't act out our dreams. If your sleep is interrupted for instance by a draft, you can experience the sensation of being conscious but unable to move.

EDIT: the mare is usually depicted as a long haired woman or troll like demon, en.wikipedia.org/wiki/Sleep_paralysis
( willenium Fist bump for verification, Mon 27 Jul 2009, 20:26, closed)