XnView Software

I just found that "Properties" of the exe have an option "Disable display scaling on high DPI settings" (in "Compatibility" tab). After I checkbox it then the problem is gone. (And I don't really need XnView enlarged anyway).
Seems that something wrong with MS scaling function.
In case you still ...

The system screen capture works as it should, giving full size pic (1440*900).

When I choose 'rectangle' and press a hotkey for screen capture, my screen gets instantly resized, so I see only left-upper part (960*600), that is now stretched to all the screen space.
After I select the rectangle and screenshot is taken (it appears 960*600), the screen gets back to 1440*900.

PS ...

Yes, the last version (1.99.6) does this too.

My screen resolution is 1440*900, but when I take a screen capture (with the setting "Capture all desktop"), I get 960*600 picture (top left corner of the screen, so the right and lower parts of the screen are truncated out).

Also, in the viewer, pictures with 100% scale are shown actually 150% (so ...