I have had the same disappointment; no 360° looping. Until I see a technical argument why it is not possible with flash while it is with Quicktime, I will consider this a bug in the flash engine. I hope it gets fixed soon.
Best regards,

I can only second the request: the possibility of 360° looping with pure cylidrical images in flash. It should be far less complicated than the 3D distortion that I sometimes find annoying. It works fine in QuickTime so for flash I will consider it a bug, really.