Hey there! Ran into a problem yesterday. After booting up, my usb mouse was powered, but not connected. Testing it with other usb devices, thumb drives, HDDs, nothing connects, but most devices are still getting power. No apparent difference between either of the two ports. I tried booting into my Windows 7 Bootcamp partition, where it at least gives me the "unrecognized USB device" error, but no better luck connecting anything. I've already reset the PRAM and the SMC with no change. It hasn't been dropped or had any spills or the like, and nothing was installed between it being in working order and not. Any ideas? Running 10.11.4, it's the 2.3Ghz Intel Core i7 model I bought refurbished a few years ago. EDIT: For any future Googlers, the problem was unresolved, and they just replaced the logic board. Anticlimactic, eh?