>This might seem stupid but are you sure it's not a bitmap?

(forgive me if this appears twice. I just lost my first attempt and I can't be sure I didn't submit it)

Yes, I'm sure its not a bitmap. Its a 16x16 96 dpi 32 bit single frame icon.
It works as it should throughout the application. It is, for example, the default form icon. (Perhaps thats the problem!)