Today, Ubuntu 12.04.1 (GNOME Classic) was giving me this error when unmounting and SSHFS drive: “mount disagrees with the fstab.”
The SSHFS syntax has changed a bit recently. I modified my fstab to the syntax below and all is well.
In /etc/fstab:
USER@SERVER:/path/to/project /mnt/server fuse.sshfs user,noauto,transform_symlinks,idmap=user 0 0