If you set Firefox 6 to not upgrade then it should not be upgrading! <br/>However firefox 6 is no longer supported or considered secure, you should be using firefox 3.6 or firefox 7. There is a particular malware that may cause firefox 7 to crash, but not 6. The problem is that malware (it also affects other browsers) will remain active on your machine (IF that is your problem) and could conceivably be considered a greater danger if the browser does not crash. It may well be worth you doing full system scans with multiple security tools/sites see * [[is my firefox problem caused by malware]] * [[firefox crashes]]