As for the reader, it may be that you simply got a bad unit. Might be worth taking a laptop down to the store and testing a replacement on the spot. That said, I've used Lexar for years with no issues.
Zoombrowser isn't the brightest candle in the chandelier, frankly, and it may be that it has buffering issues with USB 3.0, given that Canon aren't aggressive about their updates. I generally use Lightroom or Bridge to make transfers, but straight drag and drop works just fine if you don't care about adding metadata, making copies or converting to DNG during transfer.