I frequently get a flashing white horizontal line appearing in the bottom right hand corner of my Macbook's screen. It's very thin, and extends from the right edge of the dock to the edge of the screen. It seems to occur more often than not under high cpu load, e.g. viewing a youtube video in Safari, or flicking through a folder in cover flow mode in Finder. I bought my Macbook in January 2008. I took my macbook into an apple authorised service centre a few months back, assuming it was a hardware problem. They concluded that it was instead a bug in OS X (likely brought on by an issue with 10.5.2, its new graphics drivers, and the dock), as they were able to reproduce the problem on a number of other macbooks. They suggested that the problem would likely be fixed in the next update, i.e. 10.5.3, and in the meantime, I could avoid seeing it by hiding the dock, or slimming it down so that it doesn't extend so close to the edge of the screen. Well now that I have updated to 10.5.3, the problem is still there, and I'm pretty annoyed. Has anyone else come across this issue? What are my options from here?