Aspect ratio problem in preview

Display problem in viewer after clic on the image above

Image properties:
Format: JPG trucolor (v1.1)
Width: 640
Heigth: 480
# of bits: 24
DPI: 26x20
Compression: JPG
This didn't happen in previous versions of xnview, otherwise I open the image with irfanview and it is displayed perfectly. Hope you can fix it.