I purchased a refurbished 2012 MBP from Apple a few months ago. I attached am Epson scanner to it a few days ago and attempted to scan a document. The scanner would begin to move and then freeze; the software wasn't responding. I checked the software: I had the latest versions installed. After several failed attempts I began looking for a replacement scanner. I decided to try one more thing: attach it to my 2010 macPro. It worked fine. Is this a symptom of an underpowered USB port or ???