PB Display Issues. Horizontal lines around windows..

Hi,

I was wondering if anyone had heard about an issue with the display on a PowerBook. I know it isn't a problem with the display panel on the laptop as the issue is appearing on an external monitor as well.

There are horizontal lines that are appearing around the windows like breaks in the shadow (see attached image). Has anyone else experienced this problem before? Is this known to happen before on Leopard? I'm currently awaiting the delivery of a new MBP, but I'm meant to be selling this laptop so I would like to solve the problem.

Thanks all.