Did you check that the umount (without the -n flag) actually works?
Shutting it up can be a disaster on a large system.
Simon
P.S. Please ignore the below address and flame shimon@teleport.com.
He receives and answers mail :-)
Simon Shapiro Bullet Technologies, Inc.
shimon@Bullet-Tech.com 13130 SW Haystack St.
(503) 524-6631 Beaverton, OR 97005