Atheros 9280 issue

I have a Zotac ION board with an Atheros 9280 in the mini-pci slot. I
did a few tests in sta and hostap mode with 8.0-BETA4 and all seemed to
work correctly. Today I switched off my old access point and replaced it
with this new system and FreeBSD 8.0-RC1, but suddenly I got plenty (one
every few seconds) of the following error messages:

ath0: stuck beacon; resetting (bmiss count 4)

Clients can connect to the AP, but obviously packets are dropped every
time the card is reset.

Is there anything I can do to help debugging the issue?


dmesg:

ath0: <Atheros 9280> mem 0xfebf0000-0xfebfffff irq 16 at device 0.0 on pci4
ath0: [ITHREAD]
ath0: AR9280 mac 128.2 RF5133 phy 13.0


pciconf:

ath0_at_pci0:4:0:0:        class=0x028000 card=0x10671a3b chip=0x002a168c
rev=0x01 hdr=0x00
    vendor     = 'Atheros Communications Inc.'
    device     = 'Atheros AR5B91 Wireless Network Adapter (0001)'
    class      = network

-- 
Alex Dupre