That's a new one to me. It is Apple/ATI/nVidia and not likely Graphisoft, in any case.
You say 10.5.5
Try downloading 10.5.6 and see if that update helps, as it is supposed to include some graphics fixes.
(Since you have multiple machines, I suppose you know that you can download the update file once from:
http://support.apple.com/downloads/Mac_OS_X_10-5-6_Update
and then install on each machine. Best to repair permissions before running the update either via Disk Utility, or with a utility such as Onyx.)
You don't say which version of AC you are running. If it is 12, then go to Options > Work Environment > Advanced Redraw Options and try sliding 2D Drawing Hardware Acceleration to the 'Off' position. Is Memory Usage in the 'High' position?
Cheers,
Karl
AC 28 USA and earlier • macOS Sequoia 15.3, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
One of the forum moderators