I know that this problem has been discussed before, but that was for older Macs going back 2-3 years ago. Well, over the past few months I keep getting this error message and my .dmg files don't open after downloading (not all of them but quite a few). I have a PowerPC G5, 4 x 2.5GHz, running the latest OS X (10.4.10). Any help will be appreciated!