Can't decrypt WEP frame

http://mail-index.netbsd.org/current-users/2000/12/25/0005.html

$ dmesg | grep wi0
wi0 at pci0 dev 14 function 0: Intersil PRISM2.5 Mini-PCI WLAN (rev. 0x01)
wi0: interrupting at irq 5
wi0: 802.11 address 00:60:b3:6d:8c:c6
wi0: using RF:PRISM2.5 MAC:ISL3874A(Mini-PCI)
wi0: Intersil Firmware: Primary (1.1.1), Station (1.8.0)
wi0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps

With WEP configured on the above wi0 interface, I (almost) cannnot connect
from a Mac OS X box.  The Mac dumbly complains it can't connect and meekly
offers to try again.  The NetBSD 3.0 access point says it can't decrypt
the frame:

$ wiconfig wi0 -o | grep Can
Can't decrypt WEP frame:                365

Taking a hint from Peter's old message, I set the password thus:

$ ifconfig wi0 nwkey 0x0123456789

That worked: The Mac can connect, provided the password is prefixed with a
dollar sign.  

Question: When the password is instead set to 'woods', the Mac cannot
connect.  Why not?  Is there some setting I'm missing?  

Thanks for any advice.  

--jkl