I just tried the same thing with the image I made in Irfanview but with it converted to a png file and the image was black as normal. Maybe it has something to do with the software you are creating the png file in? A long time ago (in the old blitzbasic days) I used to export image strips from darkbasic as 16bit bitmaps (if you set the graphics depth to 16bit any screenshots you saved were 16bit...) and if I loaded them as an imageanimstrip they were shifted to the right for each frame by about half a frame's width.
I'd be happy to try testing this with one of your png files if you want to send me one to my email address in profile.
I'd be happy to try testing this with one of your png files if you want to send me one to my email address in profile.