Oh, and don't be afraid to rip up and start again.
The shield of the USB connector is connected to anything. I wouldn't mind seeing that connected to chassis.
USB cable shielding:Shield should only be connected to Ground at the host. No device should connect Shield to Ground
6.8 USB GroundingThe shield must be terminated to the connector plug for completed assemblies. The shield and chassis are bonded together. The user selected grounding scheme for USB devices, and cables must be consistent with accepted industry practices and regulatory agency standards for safety and EMI/ESD/RFI.