I have a USB floppy drive installed permanently connected inside the computer case.
Thus, it is always connected to USB at the time of booting the system.
I have permanently connected a KVM-41ua 4 USB Port 2.0 Switch + A USB WiFi Keyboard with mouse (which has never worked well, the kvm)
I don't have Lars's USB drivers installed
But when up to the last version of ACPI drivers, the computer start stopped. Disconnecting the KVM cables from the USB and leaving only the monitor cable, with the usb wifi keyboard + mouse, it works well.
I tell you this in case the problem can be from the aci distric and not the USB Driver.
Saludos