ifconfig ath0 mode 11g panics on netbsd-5 amd64

[Roy Marples <roy%marples.name@localhost>]

Hi List

I've recently noticed that my ath(4) powered Access Point is running at 
11Mb in 11b instead of the desired 54Mb in 11g, although I'm only using 
WEP at this point. The mode isn't changed from the default autoselect.

Issuing the command
ifconfig ath0 mode 11g
causes a panic and reboot. Here's a bt

(gdb) bt
#0  0xffffffff8054c266 in cpu_reboot (howto=260, bootstr=<value 
optimized out>)
    at /usr/src/sys/arch/amd64/amd64/machdep.c:694
#1  0xffffffff80493328 in panic (
    fmt=0xffffffff809b519f <Error reading address 0xffffffff809b519f: 
Interrupted system call>) at /usr/src/sys/kern/
subr_prf.c:253
#2  0xffffffff8054da64 in trap (frame=0xffff800046ed2230)
    at /usr/src/sys/arch/amd64/amd64/trap.c:256
#3  0xffffffff80100eea in calltrap ()
#4  0xffffffff804921ee in kprintf (fmt0=0x0, oflags=Cannot access memory 
at address 0xffffffffffffff7c
)
    at /usr/src/sys/kern/subr_prf.c:1458

Can anyone shed any light on a fix, or can I provide any more information?

Thanks

Roy