Hello extech, any luck if you clear both cookies and the cache ? Note: This will temporarily log you out of all sites you're logged in to. To clear cache and cookies do the following:

1. Go to Firefox > History > Clear recent history or (if no Firefox button is shown) go to Tools > Clear recent history.
2. Under "Time range to clear", select "Everything".
3. Now, click the arrow next to Details to toggle the Details list active.
4. From the details list, check Cache and Cookies and uncheck everything else.
5. Now click the Clear now button.

Further information can be found in the Clear your cache, history and other personal information in Firefox article.

Did this fix your problems? Please report back to us!

Thank you.

Unfortunately, clearing everything hasn't helped, nor rebooting, etc.

It is possible that some fields have the same name/id as input fields on another website.
Saved form data is not site dependent, but is stored globally without a reference to a specific web page.
So if web pages use a common name for input fields then saved data can show up on other web pages that use the same name.

Given that I'm working with name, date and place fields, that sounds entirely plausible. Any fix for that?

I tried posting the HTML for a blank form, but it's too long; I never became proficient at reading HTML source code. They have a 3-day trial for $1.95. I could e-mail the source somewhere.