Comment 5 for bug 394503

> I tried opening a PNG and it doesn't let me create a new layer.
not reproduced: opened bitmap, 'Layer > Add layer…' works as expected. (Inkscape r22288)

>If I make changes and hit save, a correct PNG is saved.
Did you try to open the saved PNG? AFAIK Inkscape can only export not save as PNG - when saved it overwrites the bitmap with SVG content, and crashes on reopening (self-referencing when loading the linked PNG?). That's bug #429529 …