Hang on - do you mean the (narrow) display cable, or the (wide) IDE drive cable? I can't see how it can be the drive cable as the only part of it that comes near the display board is the back of the drive connector on the hard disk.

The display cable, yes - it can be pinched by the drive tray which would cause this. I was going to suggest that the next thing to look at would be the display cable for chafing.