I'm facing the same problem with HP v220w 16GB flash drive. I've tried each and every method that I could find on other websites but to no resolution. I use windows 7 64bit and it is updated with all the latest updates. Other flash drives are working fine on the same ports therefore I don't see any hardware related problem. I'm out of clue now.
Try plugging the flash drive into a usb extension wire.. it worked for me. probably one of the contacts are too thin or something..