Hello,

From the mail subject I guess you are running mac osx...
The problem is that the default archive utility will
try to process the file twice :
- the first run will expand the zip archive into a jar archive
- the second run will expand the jar archive into a
folder with the class files

Possible solutions :
- control-click on the link, and choose "Save link as"
then unzip the file from the terminal
- use stuffit expander if you have it

I hope it will help...

Cheers

JF