Description of Problem:
In /usr/share/mime/packages/freedesktop.org.xml is contained the file
associations for varios types.
Also included are the extensions and in some cases magic number
support.
ASF has a magic number and extension support but WMV does not (it is
exactly the same as ASF)
but this is not the problem.
Nautilus uses this data when working with files and is causing a problem
with WMV files (ie it thinks
its and ASF with an incorrect extension and won't play it using the
association to mplayer I setup)
When you initially open nautilus and browse to the wmv is looks fine but
when you click on it, it must
read the magic number because it immediatly changes the icon to an ASF
icon which is incorrect.

Steps to reproduce the problem:
1. Download WMV file
2. Open File Browser
3. Browser to WMV file (note Icon)
4. Single Click on WMV file (note Icon)
5. Double Click on WMV file

Actual Results:
The WMV file changes to an ASF file to gnome

Expected Results:
WMV file should be a WMV file

How often does this happen?
All the time

Additional Information:
-- Fix information
I spent a great deal of time trying to get this to work and finally did
in a hackish sort of way.
Firstly I added the correct magic number info to the x-ms-wmv entry in 
/usr/share/mime/packages/freedesktop.org.xml and ran
update-mime-database /usr/share/mime
This correctly installed my changes however this did not fix the problem
(this is the bug right here)
I went back to /usr/share/mime/magic and moved WMV above ASF in the list
and it now works but 
the issue is reversed.  ASF movies change to WMV movies and won't play.

The fix should be that nautilus looks at both the glob info and the
magic info to make the correct 
decision since togeather they are very correct but appart issues can
occur like same extention 
different magic or visa-versa.

:o)