I know I'm not the post owner and this originally was posted half a year ago but think my problem is similar:
My USB stick is recognized by the operating system (Windows XP and Windows 7)
Shows up in device manager but under USB Controllers, portable devices is empty
Shows up in disk management as D: but no support
Display error "Insert a disk into unit D:" when trying to access it
All other usb flash devices works well on this 2 computers
It seems that the USB stick as some how loose the connection to memory chips.
Do you know any utility to initialise USB drives from the scratch?