@ nightrhyme:
http://sourceforge.net/projects/sevenzip
compresses tighter than almost any other tool - that's why!
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P.S.: Looks like the new .7z archives require at least 7-zip v4.2x (current version is 4.23). If it still doesn't decompress, you might have received an incomplete archive and should download again.
I was able to unpack it with version 4.20.