I'm having real problems with a new 2Ghz G5 running Tiger 10.4.1. Black boxes appear on the display at random both in the finder and when in applications.
The boxes consist of a black keyline with a transparent centre.
It's not the monitor (apple 20inch TFT). I've tried the monitor with another G5 and it works fine.
Connecting another monitor to the mac results in the same problem.
I've zapped the PRAM, done an archive and install of the OS, run Apple Hardware Test (Ha Ha but it is under warranty and I know they'll aske me that) tried changing display resolutions, all with no success.