my guess is that the LCD cable is faulty or loose inside; perhaps the ground pin is detached, and the data lines are floating.

Once sign for this is that different screen patterns can make the problem worse according to the average voltage on the data lines which makes them float/drift to a different voltage and means the sync or clock will trigger or not

just a hunch.

I've seen this sort of behaviour on my zaurus 6000 when I don't connect the LCD cable correctly.

There are photo journals around of dismantling the 800, so I would carefully follow one and carefully clean any connectors and reinsert cables to try and cure this

Anyone have any luck with this?

And now it's my turn. Luckily the N800 is now mostly employed as an alarm clock, and so the trying to hit a rolling alarm stop button is actually something of an improvement. :-)

It's kinda shocking though that Nokia lousy hardware can't survive the rigours of sitting undisturbed on a bedside table without falling apart. I was almost able to understand the touch-screen of my heavily used N810 failing, but this case is something else.

Meego buy my next hardware from someone other than Nokia.

Mine just started to happen a few days ago, I turned it off, took out the battery, rebooted, then it would be Okay for after 30 minutes, then happen again. So I think this is it, after my 770 and now my N800, this is the end of maemo for me.

Since yesterday I have the jittering problem.
This jitter was stronger with black background and white foreground, for example with N800 off and charging or with the security numeric pad logon.

However, I managed to login and the desktop was displayed without jittering even I work with some apps, afterwards I turned off the device and the jittering problem came alive.

I'll check the symptoms with more time

I'm sorry to say that your screen is dying
I think it's almost impossible to find a replacement screen now.
The one I replaced 3 years ago is still working fine, though I don't use the tablet very much nowadays.

I hope to find which is the wrong electronic component, and replace it.
I will disassemble the N800 in a short time and I will see with more detail.

I just fixed mine. There is nothing to do with the cable, just the LCD screen. I got a cheap used one from ebay, took out the LCD screen from it and put it back to my old one. Now, everything is working again. I put a new screen protector on it, and my N800 looks like a brand new one. I am so happy to get my N800 back, even though I have an Android Tablet and an Ipod touch 4. The N800 feels so solid in my hand.
I really hope more people can develop the programs for 2008OS, but I doubt it.

Where on Ebay did you find a cheap screen?

Not just the screen, a whole used N800. You don't need one with nice case or any other accessories. Just be sure the screen is nice and working.
And the disassembly is very easy, just follow the video on youtube.

http://www.youtube.com/watch?v=I3BorZkQ2Vo