7u45 is the latest and most secure version of Java. Mozilla has implemented a change that is resulting in the dialogs you are seeing. Please see this bug on the Mozilla site, you can contribute after you register:
As to the manfest warning, which is unrelated to the FF messages, see this blog posting on what needs to be changed with the application:
Thank you, Roger for replying. So this is an issue with Mozilla and not Oracle. It looks like a verbal war out there at Bugzilla@Mozilla regarding this bug. I hope Mozilla will fix this issue. Lately, Firefox has been having various issues to do with software update, the last one was Norton Internet Explorer. It is pretty scary updating software with Firefox as a primary browser.