I know this post is old already, but if it may help any new commmers.
I did this once with one of my USB flash drives. The way I fixed it was by reformatting it with either the ntfs or the FAT partition. Try this:
1. insert the flash drive into usb port
2. right click on "My Computer" > Manage - The Computer Management window popsup.
3. Select Disk Management
4. Locate your Flash Drive at the bottom where it starts with "Disk 0" which is your Hard Drive.
5. Your Flash Drive should say something like "Disk 1, removable", to the right it should have a blue line which means it's a primary partition.
6. If it has a Black line, then it means that the Flash Drive has not been partitioned. To fix this do this:
7. Right click on the black line. It should give you an option to partion it.
8. Go ahead and partition it to FAT or NTFS which ever option you can get or want.
9. Once it is finished, then you will be able to read and write from the Flash Drive.
Let me know if it does not work or if you are having problems.