I don't think you're telling us the whole story, Phil...
What is the difference between the cards that work in your card readers and the ones that don't? What type of xD cards are they? 'H', 'M', 'no letter designation'? What model Fuji camera formats the cards in such a manner that they work in your card readers?
It would appear that either your Oly cards are not compatible with your readers, or the camera formats them in a way that cannot be read by them.