O.K., thanks, you are probably right: the CMM defaulting to some reasonable internal profile would explain the apparently correct Windows Explorer previews of the specially prepared images (I'm using just an ordinary LCD monitor). And Firefox's new native CMM is probably doing a similar kind of fallback, although it would be nice if the Firefox "Console" error message window would show something about an invalid display profile. So the new CMM remains not so great after all... Sorry to have propagated hasty conclusions about it on this mailing list.