Troubleshooting Resources for USB

USB works great, when it works. How do you troubleshoot it when it doesn’t? Most other interfaces have various devices and procedures to isolate the problem, COM and Parallel have loopback connectors and test software. LAN has it’s devices for cableand device testing. USB —- Nothing.

Search Techrepublic and you find little or nothing helpful, are only a few of us having problems, or are their only a few devices in use to have trouble with?