Problems dowloading Alice 2.2

I am trying to download Alice 2.2 to an eMac running OS X 10.5.6. When I double-click the .dmg file I recieve an error message "The following disk images failed to mount." The indicated image is "Alice 2.2 dmg" and the reason is "not recognized." See the attached error message .png file.

Any help would be appreciated. Thanks!