Symptoms:

Firefox 3.5 randomly crashes on Vista.

IE8 randomly crashes on Vista.

Fix:

If you are running Kaspersky Internet Security 2009 or 2010 then remove this and try another antivirus program.

If you are not running Kaspersky Internet Security try reinstalling the browsers and disabling plugins.

In windows you can simply highlight an option and click delete however on OS X you need to click shift+delete.