Hi Phil
I see you are using /APIC with an nVidia chipset.
Which nVidia chipset? and which version of ACPI?
There is an effort to update USB controller drivers currently and it may be worth trying the most recent builds to see if they overcome the problem - although I tend to suspect an ACPI problem as you say 1 OHCI controller simply seems to go "missing" when the system has booted. The updated usb drivers are here
http://hobbes.nmsu.edu/download/pub/os2/system/drivers/misc/usbxhcd7.zipSomething else to think about: USb hubs do not show up in Resource Manager or USB Dock so what USB device(s) did you have attached?
Regards
Pete