lowercase 'm' with dummynet rate limiting ? Known issue ?

[Ensel Sharon]

Newly installed 6.1-RELEASE system with dummynet and hz=1000 built into
the kernel.

I ran this succession of commands:

ipfw pipe 1 config bw 10Kbit/s
ipfw add 00005 pipe 1 all from any to any

Great.  It works.  Things are damned slow, which proves it is doing what I
want it to.

I also want to pass the packets through after the pipe to a few other ipfw
rules, so I then did this:

sysctl -w net.inet.ip.fw.one_pass=0

Everything still working great.  Now, I want to just adjust the rate to
the bandwidth I _really_ want, not 10 Kbit/s.  So I run this command:

ipfw pipe 1 config bw 10mbit/s

Oops.  After about 5 minutes, the prompt returns, so it's not like a
normal accidental-ipfw-lockout (when those happen you never see the prompt
again).  But it might as well be, because that was the last response I got
out of that system - can't ping it, can't connect, and both ssh sessions
timed out trying to get a prompt back.

So what did I do wrong ?  I see that the man page calls for a uppercase M
(10Mbits/s) whereas I typed a lowercase 'm'.  Was that the problem ?  Or
was I supposed to remove the first pipe completely before reissuing the
'ipfw pipe 1 config' command again ?

Any idea why that command took it off line ?