Image Modification

Hi everyone,
I am trying to modify the 1.33 image with the ultimate goal of added SSH server and iperf to it. I created a new virtual server running FreeBSD 6.4, installed bash, downloaded workon.sh and the 1.33 image. I haven't been able to get any further though in modifying the image. Here is what I get when I try to use workon.sh.

freebsd64# bash workon.sh generic-pc-1.33.img
mdconfig: ioctl(/dev/mdctl): Device busy
mount: /dev/md90a: No such file or directory
workon.sh: line 30: mnt1/mfsroot.gz: No such file or directory
mdconfig: could not open tmp/generic-pc-1.33.img-mfsroot: No such file or directory
mount: /dev/md91: No such file or directory
[root@freebsd64 ~/mnt2]#

Anyone know what could be wrong? Thanks much!