I have an app that updates itself over the internet, and the updated copy won't run on PowerPC machines (G5) running Leopard (10.5.8). Double-clicking the app produces a message saying "You can't open the application "appname" because it is not supported on this architecture." But here's the weird part: if I duplicate the app using the Finder or using a cp -R command, then the duplicate runs fine! And yet, if I do ls -laeR on both apps, the results are identical. I restarted the machine, and the difference between the two copies was still there.

Sometimes, renaming the app made it run. After a few tries, I managed to rename it back to the original name and still have it run.

If this was just on one machine, I'd dismiss it as disk corruption, cosmic rays, or a voodoo hex, but it was reported by a customer and then I reproduced it on my own machine.

Any ideas what could cause this behavior?