I've removed the USB key while the system was saying something like finishing writing, DO NOT REMOVE USB stick but I wasn’t looking at the screen so couldn't catch the on-screen warning.
Now I have a stuck folder in my drive. If I try to delete it I get an input/output error in Nautilus. The stick seems to work fine though.
Any advise on how to remove the folder? Need to format the stick?
looks like there are errors on the filesystem.
follow this link:
How to repair a corrupted FAT32 file system
where they tell you how ro correct these errors. The pendrive is read-only as the computer is cannot make sense of the present state of the filesystem, and if ubuntu were to tashly write anything to it, it might cause data to be lost.
Go to format USB than format your USB to any other format. Now format it back to the format you need. This should work =)