[8.0 Beta 1] Hang after loading USB ehci drivers on Asus K8N4-E

Hi,

I meet a problem with the 8.0 Beta1 (amd64 and i386) on an Asus K8N4-E
motherboard:
During the kernel load, my system hang (no dump, no error message).
The last messages are (hand copy):
ohci0: <OHCI (generic) USB controller> irq 21 at device 2.0 on pci0
ohci0: [ITHREAD]
usbus0: SMM does not respond, resetting
usbus0: reset timeout
ohci0: USB init failed
device_attach: ohci0 attach returned 6
ehci0: <NVIDIA nForce4 USB 2.0 controller> irq 22 at device 2.1 on pci0
ehci0: [ITHREAD]

How can I found more technical information where the system hang ?

This system works great with FreeBSD 7.2.

Regards,

Olivier