When I see you report the blinking stopped after the laptop sat overnite (when 5 reboots and a new Windows install failed to resolve it yesterday), it sounds like a component needed to discharge for the laptop to function correctly, similar to removing the battery, pressing the Power On button for 30 seconds to discharge the laptop, then plugging in and starting.
Are you sure the power outlet you're using is properly grounded?
You now report a new USB issue. What steps did you take to re-install the USB driver?
If I was in your situation and still within your retailer's exchange/return period, I would return the system to stock configuration and attempt to reproduce any issues. If issues did occur, I would exchange the laptop for a new unit.
From what I've read, having to discharge the laptop prior to startup for it to function correctly is only a temporary fix to a larger hardware problem. It's best to get rid of such a system if you can. The highly unusual "blinking keyboard backlight" issue was your warning to expect trouble from this laptop...
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT