growfs says 'we are not growing' ?!?!

[Rishi Chopra]

Trying to enlarge a partition (/usr) on a slice (da0s1) with plenty of 
space:

# fdisk

The data for partition 1 is:
sysid 165 (0xa5), (FreeBSD/NetBSD/386BSD)
    start 63, size 1171861362 (572197 Meg), flag 80 (active)
       beg: cyl 0/ head 1/ sector 1
       end: cyl 1023/ head 254/ sector 63

# df -h:

Filesystem       Size       Used       Avail   Capacity   Mounted on
/dev/da0s1a     193M      80M      98M      45%      /
/devfa              1.0K       1.0K      98M      0%        /dev
/dev/da0s1d     193M     5.9M    172M      3%        /var
/dev/da0s1e     1.9G      670M     1.1G       37%      /usr

But when I try:

# umount /usr
# growfs /dev/da0s1e

I get:

growfs: we are not growing (1048576 -> 0)

What am I missing?  The /stand/sysinstall program had some problems with 
a large /usr partition as well; when I tried installing the system 
giving /usr all the remaining space on my disk, the installation would 
choke during the fetch and install from ftp.  How can I take advantage 
of the remaning free space on my disk?