You are right to be confused (my fault)
I had FF 3.6 upgraded to FF4 thats the time i got problems - I then went back to FF3.6 now my only problems are
(1) I keep getting the log-in box each time i change pages in Yahoo.
(2) when I start up I get a full page of add-ons on the screen.
I did upgrade to FF5 in the meantime in trying to solve it myself - but compatibility became an issue so went back to FF3.6.
Now using FF3.6 as stated above.