fieldset+legend padding-top is a mess in IE.
All padding-top values appear ABOVE the legend, thus pushing the entire fieldset box down (i.e. just like margin-top)
Since jar files are just zip files, I would just extract each jar file into their own directory, using a tool like 7zip, and then compare each directory.
I think this is the real problem you need to resolve (i.e. why won't it work using radio) instead of forcing to use checkboxes as radio buttons (which is not their purpose).