Hello dear users,
I had the same issues with my USB midi controllers. They were connecting and disconnecting constantly which drove me crazy.
After trying everything written above (they may be a solution for someone else's specific problem) I finally realised the problem was my desktop pc's usb ports have been used by MANY devices - old, new, current.
Let me explain this: each time we connect a device into a usb port it installs a driver (mostly automatic). Then it stays in the system. Even if we plug in a friend's usb flash disk to copy a document, its drivers linger on. So over time our machine collects many UNUSED usb port drivers. By cleaning them we avoid possible conflicts and a system speed up as an added bonus.
Here's how I did it...
I downloaded a little freeware USB port utility called USBDeview from www.nirsoft.net and ran it AS ADMINISTRATOR.
I found the unused old drivers and uninstalled them thus cleaning the list. Then restart. Plug in your device, see it is activated and have a nice day!
Best regards,
Have a nice day.