LibUsbDotNet returns garbage

I have written an application to read magnetic card readers using a USB connection. I used libusbdotnet because it links directly to libusb 1.xx on linux.

When I pull out the card, I get a lot of what I think is binary data that doesn't match the data I get when I use the hidden computer driver. The PC sees the card reader as a keyboard.

How can I fix or debug this? I tested it on my Windows system but I get the same results.