Description of Problem:
When clicking a particular MP3 in Nautilus, a
window containing the following text appears:

----------------------------------------
Cannot open Portishead - Numb.mp3
The filename "Portishead - Numb.mp3" indicates
that this file is of type "MP3 audio". The
contents of the file indicate that the file is of
type "MP3 audio". If you open this file, the file
might present a security risk to your system.

Do not open the file unless you created the file
yourself, or received the file from a trusted
source. To open the file, rename the file to the
correct extension for "MP3 audio", then open the
file normally. Alternatively, use the Open With
menu to choose a specific application for the file. 
----------------------------------------

Clearly this is wrong.

Steps to reproduce the problem:
1. Click the MP3 in Nautilus

Actual Results:
Window appears as above; mp3 does not load
(because the window has only a Cancel button)

Expected Results:
MP3 loads as normal.

How often does this happen? 
Only when clicking this particular MP3. Others
work without problems.

The mp3 is available on request.

Debian unstable on x86.