Nano USB port not working anymore

My Nano 3.0 (compatible version) was working OK for the last 2 weeks running an RGB led cube when it suddenly stopped working last night. I tried connecting it to other USB ports with no apparent success. The power LED was off and the PC / SDE could not detect it anymore. Powering it using an external 5.2V DC power supply via the VCC and GND pins made it come alive again, but it was still unrecognized by the PC. This seems to point to the USB port being the culprit here.

Can anyone suggest how I can troubleshoot this issue to find out exactly what is wrong with the USB port? Any ideas / help appreciated.TIA.

Alan

USB runs through a Diode, D1. It is possible the diode was damaged.

Thanks. Will look into that and report back.