AMR (Adaptive Multi Rate) is common audio file format for mobile devices like mobile phones, laptops, portable recorders.. etc.
in fact totem movie player can't play any amr files (files encoded in amr codec) by itself. Totem Player depends on Gstreamer libs, which haves necessary media handling components .
from your post its not clear that whether your totem can't play movie files from the very beginning or just you can not play movies recently.
your totem player may lacks Gstreamer library files or somehow your Gstreamer libs got corrupted recently.
Reinstalling Gstreamer Library file may help you.
you can find latest source version of Gstreamer on this page
(more detailed download of Gstreamer can be found on http://openports.se/multimedia/gstreamer-0.10 )