Hello, I have the same exact problem. Using Windows 7 64bit, I have the reader installed, and it worked properly before on Vista 64bit. It's installed internally, and Windows won't recognize it, it shows up in the device manager as an "Unknown Device" However, the green light does go on, but it obviously won't read any cards, and the drives don't show up at all in the "My Computer" window.
Here's another person with the same problem from another forum.
Scythe Kama Card Reader - New-System-Build - Homebuilt-Systems