You aren't switching back and forth between Firefox 4.0 and Firefox 3.6.16 using the same Firefox Profile, are you?

Create a new profile exclusively for 4.0 and create a desktop shortcut with -P "profile" appended to the target to launch that profile.

• http://kb.mozillazine.org/Testing_pre-release_versions

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

I'm a novice to computers have been using FF for about 3 Yrs, have down loaded previous FF updates before and never had this kind of trouble before. Yes I've have tried to reload 3.6.16

To see all the History and Cookie settings, select:

• Tools > Options > Privacy > History: Firefox will: "Use custom settings for history"
• Tools > Options > Privacy > History: [X] "Remember my browsing history"
• Tools > Options > Privacy > History: [X] "Remember download history"

Also check the Delete browsing, search and download history on Firefox settings.

Websites remembering you and automatically log you in is stored in a cookie.
Create an allow cookie exception (Tools > Options > Privacy > Cookies: Exceptions) to keep such a cookie, especially for secure websites and if cookies expire when Firefox is closed.

Do not use Delete browsing, search and download history on Firefox to clear the "Cookies" and the "Site Preferences"

Clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.

this was not helpful, as I can't find 'tools'! Where do I look? Everything has been very difficult since I installed the new 4. version

You can click the orange Firefox button and click the Option entry to open the Options window.

Press F10 or press and hold the Alt key down to bring up the "Menu Bar" temporarily.