From the product promo it looks like this might be a good program (not since OS 9's graphing calculator has there been a great graphing calculator at a small cost for the mac as far as I've seen), and I appreciate the author's giving a part of the profits to seemingly worth while charities. But I downloaded it, tried to mount the disk image and it failed to mount: no checksum info, says the message. Disk utility says there is no checksum info to verify. A mystery to me, how to create the sum to check when it does not previously exist. Anyone else have this problem and/or solution, or am I missing something? (I punch the recommend button since the only other choice is not to and I'm not gonna do that on the above basis.)