Yeah, I think we're on the same page. That's a feature of firefox. You can get rid of it by turning of storing of private data, or you can change the settings so that it still stores your usernames etc. but not stuff you enter into forms.
This can be accessed by going to Tools, then Options, it's in the privacy tab, in the very last section.
If you click settings, you'll see a list of what it can save and what it is saving. To remove the current entries, simple click clear private data and uncheck the boxes you don't want it to save.
Hope this helps/ makes sense