After sailing and surfing, and almost to the level of Magellan, I finished solving it by myself, by hand, as Avecrem. None of tiny applications or complicated explanations. I arose the problem last week with an external 1TB and 8GB pendrive. Both contained more than 75% of its capacity, but the number of files was not particularly large, as many of them, in both cases, were treated for bulky items from more than 100 to 200 MB.
In both cases had access to all the information, so I could make a backup disk if when the time comes, as I read in some forums had to reformat. But I kept hoping I'd find a solution without having to dump the data back into the respective devices, and kept the originals in place. Furthermore, it is noted that none of them was affected by any type of worm, virus, or other Troyani threat.
I decided to try one last option: change the letters assigned to those units. For this I used the Disk Administrator.
1-You have to log on as administrator or as a member of the Administrators group (if you're not already by default).
2-Open Windows Explorer and Computer (Windows 7) or My Computer (above) press the right mouse button and select the Manage option from the context menu.
3-In the console tree that appears, click on Disk Management. Disk Management window disks and volumes are displayed in a graphical view and a list view appears.
Move the sidebar until you can see the drive that is mapped to the external disk.
4-Right click on the drive that we want, and select Change Drive Letter and Paths option unit.
5-Press the switch in the window and select a new drive letter button.
6-We went out and reboot.
After restarting the unit can be reused writable, without any protection.
With the stick, I performed the same operation and went back to recover the functionality of both 100%.
The reason you come to this situation may be an incorrect shutdown of the unit, turn off the power before disconnecting, remove the pendrive early, or you have switched off the computer with our unit connected and log on new unit is stalled by security (I guess) in that protected status. Therefore, city always properly disconnect the external units.
Hope you might help.