Eclipse Plugin, compare ignoring white space?

I'm trying to review some documents with the eclipse plug-in in a mixed-OS environment where the files are C++ files.  When I go to look at the diffs in a given file (using the Materials pane in the Review window) it says:



    Too many differences.  

    Turn on 'Ignore White Space Option' or do a structure compare first



The thing is, there is nowhere to turn that on *before* doing the compare.  If I set ignore white space first, it doesn't seem to do that, and if I set it after it doesn't seem to reload the file.



When I do the same review in the browser it shows the differences in the files with no problem.



I've only just installed the latest Eclipse plug-in, using Eclipse Kepler.