Please describe the problem:
Upon starting to download a video file via bittorrent and saving it to the home directory, nautilus attempts to generate a thumbnail. However, since the file is essentially empty, this cannot be done. CPU usage increases considerably, as the application searches for a portion of the video file it can use for the thumbnail. 

Steps to reproduce:
1. Start a bittorrent video transfer 
2. Save the output to a directory being viewed in nautilus
3. 


Actual results:
CPU usage increases

Expected results:
nautilus to display a simple movie icon.

Does this happen every time?
Yes

Other information:
It seems that it tries to find a new thumbnail upon every modificatÿxÌof the file too. With frequent writes, this also eats CPU time.