Panic with wi0 scan

Just put in another PCI wireless card (Netgear MA311), which is recognised
as

wi0: <Intersil Prsim2.5> mem ...
wi0: using RF:PRISM2.5 MAC:ISL3874A(Mini-PCI)
wi0: Intersil Firmware: Primary (1.0.7), Station (1.3.6)

However, an 'ifconfig wi0 up scan' causes an immediate panic:

# ifconfig wi0 up scan
panic: ieee80211_newstate: bogus xmit rate 0 setup

cpuid=0
KDB: enter: panic
[thread pid 22 tid 100014 ]
Stopped at      kdb_enter+0x2b: nop
db> trace
kdb_enter
panic..
ieee80211_newstate(c16b125c,4,ffffffff,c16a8400,380df) at ieee80211_newstate+0x50e
wi_newstate(..)
wi_info_intr(..)
wi_intr(..)
itrhead_loop(..)
fork_exit(..)
fork_trampoline(..)

ps shows process 22 as '[CPU 0] irq11: ifpi0 wi0++'

HTH someone,

Brian.