Re: In/out-error document disappeared, help appreciated
Yes, you need to unmount it first.
When unmounted, run:
(that's a lowercase L at the end, not an uppercase i)
This will give you a list of connected disks; find the line that corresponds to your flash drive and look at its Device, which will be something like "/dev/sdc1"
Put that device file into this command:
sudo fsck /dev/sdc1
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.