Looking at some of the google links, apparently this is a Mac problem. Did you try some of the other apps mentioned in the Apple support thread i.e. Springy and Untar?

https://discussions.apple.com/thread/2459752?start=0&tstart=0 

You may have to get it on a PC or last resort, try to get Kimber89's permission for someone to send you the individual files. 

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken