Macintosh G5 Display errors

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.

Comments appreciated
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Hi macjimlin,
    Have you tried to use any Color Synching or Calaboration tool on this computer?   It almost sounds like some program of that type is running in the background, maybe it never got finished, or maybe you installed something that had it come up if it detects something?
      Can you give more information of these black boxes?   What you say "black keyline" what do you mean?

Steven Stuart
You might have a bad video card or processor. If it's still under a year old, go NOW and purchase the AppleCare extended warranty. If you are unable to track the problem down, this will prove much less expensive than paying for the repair later.

If you have a compatible video card from another machine, pull it and test. It may be processor related as well.

Take it to an Apple Store and have them run a test.

Also try the Hardware Test option on the CD's that came with the machine.
How big are the boxes?
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I had a similar-sounding situation (box artifacts on the screen) after installing two 512KB memory chips in a Mac G5 dual 1.8.  Running the Hardware Test detected no errors, but removing the memory also eliminated the phantom boxes. I also experienced program aborts (iTunes).  I bought and installed a better-quality memory and have had no further problems.
macjimlinAuthor Commented:
It turned out to be VoicOver which can be switched on by Command-F5 - an easy thing to do by accident when you're using shortcut keys. I am surprised (but not massively so) that neither the Apple helpdesk nor the supplier technical staff knew about this. I wish I had discovered the solution before following their advice and doing a full erase and install!
The black boxes were not "displaying at random" - they were displaying when the user pressed command-f5. When you press command-f5, the machine starts talking to you, indicating what's on the screen and announcing every key pressed.

This doesn't sound "random" to me, but very obvious. Obvious, that is, if the volume is turned up.
macjimlinAuthor Commented:
Sorry pike480, should have clarified. This was one of 10 Macs in an office that I look after. User habitually works with sound turned off so it was not obvious. Also, due to something I do not yet understand, the boxes were displaying in a random fashion i.e. they did not alwys highlight the icon on which you had just clicked.

Thanks for all the comments.
Closed, 500 points refunded.
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