A little help, please?

I'm having a problem doing the sfdisk. It gives me this error:

BLKRRPART: Invalid argument
OK
Warning: start=63 - this looks like a partition rather than the entire disk. Using fdisk on it is probably meaningless.
(Use the --force option if you really want this.)

(Edit) Looks like someone else just had the same problem, heh. In any case, I am using sfdisk, but it keeps telling me that "fdisk" part.

Also, tried umount again, and it's telling me that's also invalid.