I've been researching the breakage of playing back mmsh streams in rawhide (with the necessary 3th party plugins installed) and I've come to the conclusion that this is caused by totem no longer passing get parameters in an URL through to gstreamer:

Using Fedora 9 with totem 2.23.2 (from Fedora 9 updates) opening the following
url works fine:
mmsh://av.rtl.nl/web/components/actueel/editienl/2008/week33/vr18.Editie_NL_15-08-2008.MiMedia_WM_1500K_V9.wmv?MSWMExt=.asf

And using gstreamer debugging I can see the full URL gets passed to mmssrc

Using the same Fedora 9 (and thus 100% identical gstreamer) with totem updated
to 2.23.4 (from rawhide) and having the rawhide evolution-data-server parallel
installed to the F-9 one for deps, opening the same URL, only the following
part gets passed to mmssrc:
mmsh://av.rtl.nl/web/components/actueel/editienl/2008/week33/vr18.Editie_NL_15-08-2008.MiMedia_WM_1500K_V9.wmv

Notice the missing: "?MSWMExt=.asf" at the end. This breaks playback of mmsh
video streams.

Note I've also reported this upstream (which I know ends up at the same person, but I wanted to make this block the F10Target tracker).