Using Mac OS X Lion 10.7.3 and Firefox 11.0 browser.
While actively completing online forms, the screen clears and reverts back (never saving it) to the blank version of the form.
Or, while composing email, it saves automatically which is OK but it removes the email as I'm still writing it. I can usually find it in the draft folder.
Or, while visiting a website, I'm reverted to the prior page even though I didn't take any action to go back.