Go to my computer, in the address bar press the downward arrow. This is going to open a dropdown menu with all the Desktop, C: and other drives and such. Search for your pendrive in these options and click on it. This always works for me when i cannot access it directly. This is probably due to a virus infection. You can fix it by removing the virus or reformating the pendrive.
Hope this works
Guillorama, May 2008