Having awoke one night at about 4:00 am, I was immediately aware of a white featurless figure kneeling beside me. I experienced a feeling of sheer terror and paralysis. This lasted approx. 1 min before I somehow fell back into a deep sleep. I would have put this down to a dream but I havnet remembered a dream since a postman pat one when I was about five and I had been able to read a title on the tv set I had left on (apparently you cant read in a dream?)

Old Hag/Sleep Paralysis

I was wondering if anyone has had a similar experience and could tell me what they think it was.

I have had many similar experiences though mostly a lot less visual, except for seeing through my eyelids which is normal. I have only had the vibs with SP a few times but whenever I've had the vibs it always accompanied by a slight calmful SP. I have even been haunted while awake and only shortly after an SP. Once I awoke from seeing a light in my computer screen and I was just standing there watching it dance before dashing out of my room in fright. I'm not sure but I thought nightmares are supposed to stop when you awake.

I think these experiences are most likely hallcinations due to the REM state that people are in during this though it is possible that some of these are psychic attacks or astral entities. You are suddenly draged from your peaceful sleep into your motionless body, sometimes with difficulty breathing. It seems very likely that it would cause a "bad trip" and cause you to induce hallucinations.
Though it is interesting how the experiences are similar in different cultures and countries. Maybe there is a common "trait" that we all share which causes these experiences.
What interests me most is the vibrations. What causes this? Could it be hightend awareness (either of the natural vibrations of your body or some non-physical body) or an hallucination. I have thought, asked and searched for answers to this and found nothing.

"In many cases, the presence is actually visible (the eyes are often open during sleep paralysis)"
Are they assuming that just because you see everything around you as though you're awake that you must therefore have your eyes open? I'm almost certain that this isn't the case. Is it really that hard to believe that your mind has a memory great enough to remember how it's surroundings are just before sleep and then retrieve them for SP? I have had many experiences when I have had SP while still having perfect vision and moments later remember opening my eyes, and I'm sure that it was no hallcination. I have even feel asleep in class without even realising it. I suddenly realized that I had stoped writing and I couldn't move. I was able to get out of this easily and people said how I was actually asleep. I also think I remember a sleep study done where it was discovered that sleep paralysis can happen while your eyes are closed.

Sleep paralysis has seriously f***ed with my mind and i've only just sarted to feel safe while in bed. I would just lie there thinking of what other horrible things that could happen to me while asleep.
I hope this wont become part of your regular sleeping pattern.

same... I used to have these often when experimenting with contacting the dead and entering the astral... usally upon returning this would happen to me...

"apparently you cant read in a dream?"
Well if that's true then I must have actaully taken the challenge to train a race horse.

Apparently you can read but its very difficult!

Reading

I personally remember kicking a ball in my grandads back garden i remember the weather, who was there what I and they were wearing the colours and the sounds, that was from when I was 6 so it must be possible for your brain to remember your exact surrounding from only a few hours ago.