Sometimes when I have had a usb memory stick plugged in to transfer photos or other files, I can’t eject the stick using the context menu.
Here’s an easy workaround for this problem:
Open a terminal session and type:
sudo fdisk -l
Enter your password, and it will give you a listing of your disk devices. You need to find which one is your usb memory stick. In my case it is /dev/sde1
sudo umount /dev/sde1
Your sudo access lasts for several minutes, so it won’t ask for your password again, it will return you straight back to the prompt without appearing to do anything. However if you type the same command again it will say:
umount: /dev/sde1: not mounted
Which proves that it was mounted the first time you ran the command.
This workaround won’t stop it from happening again, but it is an easy way of making sure the stick is unmounted before you remove it, and it saves you from potentially losing data