I've used a variety of card readers, including a Sandisk dual Compact Flash and Smart Media version.
It would read Smart Media cards, and most of my Compact Flash cards... but NOT Sandisk Compact Flash cards! I fought it for a week, reinstalling the drivers, etc, and finally contacted Sandisk support. After a week they replied that there was an issue between that version card reader and their own cards. They offered to replace it with a Compact Flash only reader. I declined, I wanted the Smart Media reader. I went out and bought another card reader (a PNY) and it worked flawlessly on ALL compact flash cards.
Just goes to show you, sometimes even the "experts" screw up...