Display distortion problems

[altair]

Just yesterday my T40's display started becoming distorted every once in a while. The best I can describe it is the horizontal lines of the display would go out of alignment and start to wiggle around. Here's a picture:

http://www.rhythm.cx/~steve/tp.jpg

It isn't consistent. It might not do it at all for 10 minutes at a time or it might get really bad and do it consistently for half an hour straight.

I have not been able to correlate this with any heat or system usage. Sometimes it happens within minutes after power on or while the machine has been sitting idle for an hour.

One thing that does seem to have a positive effect is squeezing down hard on the top and bottom of the case on the upper left hand side (like near the escape key), flexing it a bit and holding it that way (made easier since I have the case mostly disassembled right now). Swinging the display forward and back has an effect too (but then it comes back after you stop moving the display).

I have wiggled the video ribbon cable around while it was happening with no effect.

If I connect an external display, it has no problems (even while the internal one is showing the same image).

This can happen with display settings in just about any mode from 1400x1050 to text.

It started happening while using it in the car yesterday and opening the display a little farther than I normally would for desktop use (though nothing unreasonable).

Anyone see this before or have any suggestions?

[altair]

Just an update to this, I found a workaround: by underclocking the video chip's core frequency this distortion goes away completely. I underclocked from 250mhz to 100mhz... haven't tried other speeds yet.

I guess I need a new motherboard.

[roberts5]

Any update on this. Similar problem.

[altair]

Any update on this. Similar problem.

Underclocking the video chip as described has kept the problem away.

Oddly enough, when I have two monitors connected at once I must also underclock the CPU otherwise the problem starts again after the machine is on for a few hours. But when on the builtin display only I can run the CPU at fullspeed, video core at 90mhz, video RAM at 200mhz and it is fine.

I bought a new motherboard off of ebay which had working video but the sound was broken, so I sent that back. I'm just living with this as is for now.