We had a pretty nasty bug in OS X 10.1.x (which didn't seem to impact 10.2 or 10.3) that caused downloading to crash the browser. I hope tomorrow to be putting out a Mac Mozilla 1.5.1 release which corrects that problem. If you can't wait until then or you'd like to help me test this build, you can get it here. This will be a Mac-only release and really only intended for pre-10.2 users. There are no other significant fixes besides this download crasher fix.
