"Underneath this Amarillo Sky..."

GUYS really important question. I am thinking of updating to Firefox 4 because I have 3.6 and it is glitching really really really badly for me, but I don't want to update if I'll lose LJ Login. Is there a version of LJ Login that's compatible with 4? I really don't want to lose all the journals I currently have saved in, because, frankly, I don't remember half of the passwords to these journals any more.

THIS IS OBVIOUSLY OF THE UTMOST IMPORTANCE. THANK YOU.