History not deleting

Hey guys how's it going, I have had my macpro for over a year now and never was able to successfully delete my history or anything from firefox. I go to tools>and clear recent history and select EVERYTHING, that does not work. I go to firefox preferences click on privacy and try deleting there and that doesn't work, and I even tried using Onyx and that didn't work, haha. Any suggestions?
Thanks in advanced

When you used Onyx, did you first repair Permissions with it? It would seem that you're shut out of Firefox (which version?). To prevent a buildup of History, set the time you wish to keep a record of sites visited to 1 day (or 0, if you want to be drastic).