EMI problem with DIY Cintiq project

[humblebee]

For those who've never heard of a Cintiq, it's basically a digital tablet and a screen combined, which allows the user to draw on the screen. I'm pretty new to electronics, so pardon me if I didn't word the things correctly!

What I've done so far is pretty simple, just placing the components on top of each other (top to bottom):
- Screen (LCD glass, filters, and the slab of glass for the LED backlight) with a row of LED on the top edge, as well as a long PCB with data cables connecting to the screen.
- Tablet PCB
- Foam
- Metal sheet (not sure what it's for, but it came with the tablet)
- Foam
- Controller/power supply

Everything worked fine EXCEPT for a jittery cursor. The symptoms are worse as I move the digitizer pen closer to the top edge of the screen, to the point that it would have a crazy spasm and randomly click and right click. The spasms are spread out along the entire top edge, so I don't think the power supply causing the interference..

I had to turn off the power of the screen to properly map the tablet area, so these problems only occur when the screen is turned on.

I'm guessing there's some EMI somewhere on the top edge, where the LED's are or that PCB connected to the screen with all the data cables etc. But not sure exactly where.

Any ideas what the problem really is, and/or how I can go about solving it?
Thanks!!