Gettin a bmp file instead of a png

[Foxkatt]

Hi, I've been having an issue with rendering when I'm using the 208_3DHack. For some reason, instead of getting my usual png files, APO has been rendering the flames as bmp files. The render dialog box shows that I've selected png for the file. The is driving me crazy as I've never had this happen in years of using APO.

Is there somewhere I should be checking the settings? Can anyone help?

Thanks!
Foxkatt