In case you didn't see it, you should be aware of this exchange quoted from MMT3' first linked source:

Quote:
Ira Lansing
Re:
When I download the installer and open, I get this message;
"There may be a problem with this disk image. Are you sure you want to open it? Opening this disk may make your computer less secure or cause other problems."
Anybody else?
Yes, I saw that as well. I thought it might have been because I stopped and started the download a couple of times and thought I had finished but hadn't. When it was completely downloaded it did go through the installation process with no apparent problems that I could see.

I'm running Snow Leopard, and I got the same warning; it came up before the dmg opened.

The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire