I have a feeling that the electrical connections for the CF-IDE are easier than they would be for MMC/SD - IDE.
Or do you have an MMC-IDE adaptor?
Equally this document is talking about attaching a CF card to an IDE 'slot', not the other way around, though it might work I suppose.
I remember the handhelds.org devcluster used IDE HDDs that were connected via the CF slot (possibly with some kind of PCMCIA adaptor, I'm not sure), which might be of interest.
Si