Disk Image Mounter problem in OSX 10.5.8?

[rpprdud]

I am currently using OSX 10.5.8 Leopard and have run into a problem. When ever I attempt to mount a .DMG file, Finder goes unresponsive and will not re launch. The .DMG is downloaded from a verified clean source and the default program to open is the Disk Image Mounter Utility. I try going to /System/Library/Core Services, and I see the Disk Image Mounter Utility listed, yet when I attempt to open it, nothing happens and it is not even listed in the activity monitor. I have tried mounting several .DMG files and each time the same problem occurs and can only be solved by rebooting the system. I have just recently tried updating my software to the latest version and still no fix. Any help is greatly appreciated!