Try following this steps: (I don't have english version right now so names may vary from what you'll see)

1. Go to www.getfirefox.com and download latest stable version.

2. Go to menu: Bookmarks => Show all bookmarks (or Ctrl+Shift+B)=> from menu "import & backup" (or smth like this) choose to make backup copy (*.json file) and choose where to save it. Now just to be a bit more sure from the same menu choose to export bookmarks (*.html file) and again show where to save it.

3. Go to menu: History => Clear history (or Ctrl+Shift+Del) => choose to clear all history from drop-down menu and click show details. Now check all boxes and click "clear now"

4. Now uninstall Firefox via Add/Remove Programs (from Windows Control Panel)

5. Delete "Mozilla Firefox" folder (most probably it's on C:/Program Files/Mozilla Firefox/)

6. Restart Windows

7. Install Firefox from file you downloaded (in 1st step)

8. Run Firefox and import your bookmarks (like in 2nd step but instead of backup, choose to recover from file and find your previously saved *.json file. If you encounter any problems with *json file, try to import bookmarks from *.html file)

9. Adjust settings to fit you, and install extensions/addons you like.

10. Enjoy Firefox, that should be version 8 now :)

• If the above won't help, than it must be something paranormal with you ;)

Your UserAgent string in Firefox is probably messed up by another program that you installed.
http://en.wikipedia.org/wiki/User_Agent

type about:config in the URL bar and hit Enter
If you see the warning, you can confirm that you want to access that page.
Filter = general.useragent.
Right-click the preferences that are bold, one line at a time, and select Reset.
Then restart Firefox

Thank you so very much. That helped!!!!! Problem = solved. Yes! Finally.