"One or more partitions are busy on /dev/sd*" what to do?

Question

I recently bought a 4GB USB Memory, Serioux, Data Traveller. Today I wrote on it Linux Mint 13 Cinnamon edition, and now I want to format it.

I have tried to go to Disk Utility, select it and press "Format Drive", with the "Don't partititon" option, but when I click Format, and again , it gives me this message:

One or more partitions are busy on /dev/sdc

I have already tried to safely remove it and rebooted the system n times, but it is not working.

Solution

I believe it's being automounted. You can't format a mounted partition.

In Disk Utility click on "unmount" and then click "format".

"safely remove" will not let you format the USB stick, because it may actually unmount the drive and then tell the interface on the USB stick to power down. After selecting this option you can normally do nothing with the device until it is removed and inserted again (which will cause it to automount again...)