Hello.
Cache cleaning is not working in Firefox
if you change temporary files directories,
in about:config by adding strings
'browser.cache.disk.parent_directory' and
'browser.cache.offline.parent_directory'.
Personally I use free CCleaner 4.02 now, Firefox 21.0 and Windows XP Prof 32-bit SP3
but I think it does not matter in this case.
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Regards
Marcin