Have you tried "search" and target a file you know is on there, to see if it can see it? If not, then clearly something is blocking your access to the stick. It is possible you have accidentally hidden them
I found this on a website where somebody had the same problem:
1. click start>>run>>type in "cmd"
2. type the location of your flash drive.. e.g. "d:", "e:", "f:", etc..
3. type "dir /ah"
*you will now see the files/folders with hidden attributes
4. type "attrib [name of file/folder] -r -a -s -h"
*if you're going to unhide files, you should type the whole name plus the extension (format).. example "attrib party.jpg -r -a -s -h"
**if you have folders with 6 characters and above, type the first 6 characters then "~1".. example for folder named "birthday"
"attrib birthd~1 -r -a -s -h"
5. you should repeatedly type dir /ah after unhiding some files/folders so you'll know if they're now working or not..
6. now check you flash drive.. it should be there..