Can't open as layers

[mandybb]

hi, ok i'm new here. but i just started using gimp to make gifs and when I was initially making my gifs using open as layers for my frames it was working but suddenly it doesn't work anymore and whenever i try to open my images as layers it looks like this instead. 
and i have no idea what it is I'm doing wrong, so if anyone knows that'd be a great help (to clarify the images I'm using are all png files)