Unable to umount ext3 partition

[Rift``]

Hi,
I'am runing on FreeBSD i386 6.2.
i have an usb disk with an ext3 partition.
I mount the partition with "mount_ext2fs /dev/da0s3 /mnt/ipodlinux", but when
I tried to umount the disk i have: "umount: unmount of /mnt/ipodlinux
failed: Device busy". I have tried to get who is accessing to the fs,
but nothing is accessing to the disk (verified with lsof/ps).
Thanks for the answer.
Rift