Interrupt load high after 73 minutes uptime with ath(4) hostap

[Martin]

I'm running:
FreeBSD 5.3-STABLE FreeBSD 5.3-STABLE #0: Mon Jan 31 00:54:51 CET 2005
i386

The card is (Netgear WG311T):
ath0: <Atheros 5212> mem 0xe7000000-0xe700ffff irq 9 at device 15.0 on
pci0

After about 73 minutes uptime my PC is busy processing interrupts.
Top shows 90% in IRQ. Everything is slowed down. Earlier kernels
showed same effect.

When the problem appears, I start "ifconfig ath0 down" then
"ifconfig ath0 up" and everything is ok again for a certain
period of time.

Further info:
IRQ 9 is being shared with ACPI (I tried to turn off ACPI, no effect).
Earlier it was shared with my VGA-card, but showed exactly the same
symptoms.

The high interrupt load is not being reported like e.g. an interrupt
storm on lpt. The system is simply slowed down.

Martin