Because Firefox 4 is no longer supported and is not secure your recommended options are to use Firefox 5 or Firefox 3,6. Before you consider anything else it is worth using the feedback button on Firefox 4 of 5 to report the problem that you are having, If you consider downgrading Firefox read [[installing a previous version of firefox]] It may well be worth downloading, installing and running [https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ compatibility reporter] that forces some Add-ons to work, and also reports the issue to developers. Some Add-ons do actually work with Firefox 5 if you force them, others have problems, but generally most that work with Firefox4 will work with Firefox 5. I note from the DAP (Download Accelerator Plus) site that a trial [http://www.speedbit.com/beta/ Beta version 9.7] is out that is specified as compatible with Firefox 5.