I confirm this bug (reproduced via the isolated test case in Ewen's second comment) on several up-to-date Dapper systems [Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.9) Gecko/20070102 Ubuntu/dapper-security Firefox/1.5.0.9]
Workaround: disable "Remember passwords" and "Save information entered in forms..." in Preferences -> Privacy (as it was in my case since the published vulnerabilities), and Firefox won't crash at such occasions.
I confirm this bug (reproduced via the isolated test case in Ewen's second comment) on several up-to-date Dapper systems [Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.9) Gecko/20070102 Ubuntu/ dapper- security Firefox/1.5.0.9]
Workaround: disable "Remember passwords" and "Save information entered in forms..." in Preferences -> Privacy (as it was in my case since the published vulnerabilities), and Firefox won't crash at such occasions.