Poking around, I discovered that my Chumby seems to normally use a 9 Mb/s bit rate on the rausb0 adapter. I'm sure this is fine for the sorts of things the Chumby does, but I'm curious as to why it would be set to that, rather than 54Mb/s.

I used iwconfig to set the bit rate to 54M and see no problems, but I don't imagine that will survive a reboot unless I do something special.