Boot hangs up when USP plugged

[David DEMELIER <demelier.david%gmail.com@localhost>]

Hello dear NetBSD users,

I'm running NetBSD 5 on my old desktop, it has a sis based chipsed
mother board controller, and this one has many troubles with USB. Long
time ago when I plugged USB keys/ hid devices the system freezed (such
as Linux, NetBSD and FreeBSD). This is solved by playing with USB
legacy support in the bios.

But recently I kept my USB mass storage plugged in and shutdown my
computer, and when I tried to boot, netbsd's kernel stops at

[...]
ehci0: interrupting at ioapic0 pin 23
ehci0: EHCI version 1.0
ehci0: companion controllers, 2 ports each: ohci0 ohci1 ohci2

And I need to hard reboot, unplug the USB devices and then it boots well.

Do you have any workaround to fix this small issue ?

Best regards,
David.