I am glad you got it figured out.
And this was a lesson for me as well.
I know very well that when one is troubleshooting a WiFi problem, the very first step is to completely disable whatever encryption/security measures may be in place (since security measures are often the CAUSE of WiFi problems), amd make sure the WiFi connection is solid. Only then work into the encryption/security measures.
I am sorry I did not think to apply that reasoning with your USB connection issue. I should have (and will from now forward) made mention of disabling any possible security measures in place on one's PC when diagnosing such a problem. Windows 'permissions' issues are often the first cause of something not working intuitively. After all, when it comes down to fine detail, WiFi and USB are simply alternate methods of gaining access to files, so troubleshooting either method would employ the same basic steps.