I'm having trouble with colour operator logos.

I am sending the content response of "image/vnd.nok-oplogo-color" and then displaying the 100x50 gif file (which I have also renamed to .olc and .nol to no effect).

When accessing the file using a Nokia 7250 or 3510i, the mobile states "operator logo received", you goto view or save, and all that appears is a yellow question marked box.

Can anyone help?