_ Dear member of SanDisk Community, welcome. _
Please, make the following tests:
1- In the _ Control Panel / _ Administrative Tools / Event Viewer: see if there is information on this item.
2- See also, in the Task Manager , the processes which are running, and see what are the necessary and what to delete. Because, there are some programs, that cause, system conflicts, by blocking the ports, such as: Samsung Kies, HTC Sync, etc.
3- In the _ Control Panel / Administrative Tools / Computer Management / Device Management Tools:_ see if a _ USB icon _ is crossed out with red , or there is a yellow question mark, etc.
See, also, for a teaching with images, the links:
Luck, and then you tell us, what happened, please.
Regards, Alfred. (Google translated)