unexplainable totem 64 bit en 32 bit experiences

[Alexander Volovics]

I have totem installed on an intel dual core 2 pc with fedora.x86_64
and on a inspiron 6000 with fedora.x86.
Both setup with all the extra and livna gstreamer plugins.

On the x86_64 totem setup I can generally play mpeg, wmv, avi files
through firefox-1.5.0.9 without problems though somtimes the quality
is not optimal. Occasionaly totem-mozplugin opens on a white screen
and the video is 'stopped' but after clicking on the 'reload current page'
button it starts up and plays to the end.
Sometimes (why?) the video does not run in a firefox window but a
seperate small totem window is opened to play the video.

On the x86 totem setup the videos never play!
The same white firefox window is opened through totem-mozplugin
and the video 'stopped' but the reload button can not get it to play here.
Occasionaly I get a video that shows a tiny 'flash' at the start but
then continues with a black screen and the slider moving to the end.
In this case I can hear sound perfectly.

Here are some examples:
http://www.ibiblio.org/openvideo/video/cmu/UGS13_002.mpg
http://www.ibiblio.org/openvideo/video/cmu/UGS13_003.mpg
http://ia300138.us.archive.org/2/items/AtomBomb1946/AtomBomb1946.mpg
http://ia300220.us.archive.org/3/items/CongressionalAdmission/Government_and_military_perverts.wmv
http://ia300220.us.archive.org/3/items/CongressionalAdmission/WhatWouldYouDo.wmv
http://ia300203.us.archive.org/2/items/MCA-I_PSAs/MCA-I_PSAs_128kbps.wmv

Can somebody explain why the same videos play in the 64 bit setup
but not in the 32 bit setup. 
Could the hardware difference (nvidia GeForce 7300LE versus Intel 915GM)
have anything to do with it?

Please no replies plugging mplayer, etc. I have used mplayer
in the past but now I want to continue using totem/gstreamer.
It is not included in the distro for nothing.

Alexander