XnView Software

I have XnView set to default to browser view. I also have the preview pane on. Often when I open a new instance of XnView and immediately middle click on a thumbnail to view the image in fullscreen, it doesn't work. Nothing happens and there is also no image in the preview pane when this occurs. As a workaround, I have to deselect the thumbnail and try it again to get it to work. This even happens to small images. Perhaps this bug is related to slow response of the preview pane and thus causing interference? Please fix.

XnView 2.39
Windows 7 x64