Not cleaning Firefox

I have version 1.5.04 of Firefox. I recently installed CCleaner 1.30.310 which states that it cleans Firefox.

Under applications, I have all the Firefox options checked yet after running CCleaner, the report window shows: Firefox/Mozilla cache cleaning was skipped.

This will happen if Firefox is not shut down prior to using CCleaner. Close the browser completely and then run CCleaner. Hope this helps and welcome to the forum. :)