What exact error message do you get when trying to mount the LimeWire disk image, if any at all -- and, if there is no error message, what exactly happens? Icon bounces in the dock then disappears? No icon at all? No feedback at all from the Finder? Log messages in the Console? Screen turns green then spits swiss cheese out of the optical drive?
Help us help you. We can go on and on trying to guess what exactly you're experiencing all day, or, you could tell us precisely what you're experiencing.
Saying "LimeWire won't even load at all" is too vague... like taking your car to the shop and saying, "It's making a funny noise. What, precisely, is wrong with it, and what is the definitive fix for this generic funny noise it's making?"