CF card and Apple iMac incompatibility?

I do a lot of image editing, using my iMac desktop and Adobe Lightroom software. I take photos with Canon DSLRs which use CF cards. I have three types of Sandisk CF cards: 4 GB Extreme III, 8 GB Ultra and 16 GB Extreme UDMA. None of them are able to download to my iMac using the Sandisk 8-in-1 Imagewriter reader. They all work with my other Windows laptop however.

I have taken my iMac to Apple store three times (last time today) to find out what is wrong (I had other issues with Safe Boot which was resolved) and the last time I was told that CF cards is “old technology,” and that the tech has seen a lot of this problem with Macs brought in. I wonder if this is true and, if so, is there a patch or update put out by Sandisk?

It seems that most DSLRs use CF cards, although I believe Nikon DSLRs use both CF s well as SHDC cards.