Backround environment not being saved

[JJG]

I seem to have fucked up and pressed something somewhere which disables the saving of the backround image when saving out a beauty pass.
Instead it will put alpha where the image is supposed to be.
I can for the life of me not remember what I pressed. I can still see the backround environment in the render window but when saving it will save alpha instead.

Any help would be greatly appreciated because this is driving me nuts.

[JonG]

If you're saving the image as a PNG make sure to uncheck the alpha channel tick in setup.