Your kernel/firmware (operating system) has to be updated to support the new USB/Ethernet controller chip! The annoying thing is that to upgrade you kinda need network connectivity which you can't get if USB/Ethernet is down. If you have a spare Model B around, try running

sudo apt-get update
sudo apt-get upgrade

To update to the latest kernel!

No! We originally thought there might be a SEPIC/Buck-Boost 5V supply but there isn't! So if you're having power problems, make sure you have plenty o' solid 5V power and try a shorter micro USB cable. Long cables with thin wires are the bane of Pi!