Zoom pull downs vanish and scroll wheel disbled

[Richard Swann]

I have a wierd problem, Can't find any mention of this in the search of this forum:
While working on ArchiCAD yesterday at home on my G4 (466- yes I know it is underpowered, but never had a problem before), OS Tiger, AC9 I got the following problem:
Screen redraw stopped working fully on a very small file (about 8MB archive) and text and fills all appear for a nanosecond and then disappear. Rebuilding and saving did not bring them back. Had to relaunch AC and then it was OK... BUT..... the ZOOM IN and OUT from the pull down menu vanished. Both are also now missing from the keyboard shortcuts in the working environment menu and my explorer mouse scroll wheel can pan but suddenly not zoom. Stranger still I sent a PLA of the file to another G4 running Panther and after a few minutes exactly the same thing happened. The problem is that I can't clear the fault with open 'New and Reset', only by quitting and restarting the computer.
The file I have been working on includes a complex GDL script I am writing that writes to an external file, but I cant see any other reason for it to do this. Does anybody have any suggestions or is this a bug?