I'm running OSX 10.3.9. I've tried to download quicktime 7.0 (and other programs) but every one of them the disk won't mount and I get a checksum error. Any help in this would be greatly appreciated.
What machine do you have? I encountered this with my father's G5 when I upgraded it from 10.3.3 to 10.3.9. The problem was that I didn't install the firmware update available for my father's G5. Once the firmware was upgraded, things went back to normal. Check this chart out for the firmware you need.