Checkerboard.. why?

[RustyBolt]

I loaded an RGB image which I added an Alpha channel to and then decomposed it. I pasted another image into the alpha channel and then did a compose into an RGBA image. At this point the image it shows me on the screen now has a checkerboard pattern on it even though none of the channels had any transparent areas. I saved the image as a png. If I open it with a different program it appears normal. If I open it with Gimp, it as the checkerboard pattern on it.

I am new to Gimp, so I would lke to know what this is indicating and how to remove it?