User-Agent:       Mozilla/5.0 (X11; U; Linux i686; fr; rv:1.8.1.10) Gecko/20071126 Ubuntu/7.10 (gutsy) Firefox/2.0.0.10
Build Identifier: 

Just after having installed Ristretto, I was trying to use it  (and enjoying ;-)). 
But I saw that previews of the thumbnail were stretched to the border, as a square.
It happened with pictures JPEG of many sizes, PNG and GIF. I don't try with other format.
After viewing a picture, the corresponding preview got a good ratio.


Reproducible: Couldn't Reproduce

Steps to Reproduce:
1. Install
2. Browse a picture's directory
3. See at picture's preview, in thumbnail.

Actual Results:  
After a reboot, there's no any more problem in ratio of previews. 


Xubuntu Gutsy.
ristretto 0.0.13
( 0.0.13-0ubuntu1~gutsy+ppa1 from Xubuntu-team's PPA)

I hope, you'll understand... my english is a bit poor! ;-)