I have bizarre behavior with my MSI GS70 laptop running Ubuntu 13.10.

If I turn on the machine with no USB devices plugged in and select Ubuntu from the Grub menu, it hangs at a blank purple screen. It does this even if I add "nomodeset", "vesafb.nonsense=1", "nosplash".

However, if I plug in a USB mouse and turn the machine on, Ubuntu boots normally into Unity. How does that work? How can I set it up so that I don't have to have a USB device plugged in every time I want to boot?

Once the machine is on I can sleep and wake the machine just fine. It appears to be a problem only during boot.

For reference, this is an Optimus machine; I'm running nvidia-331 and bumblebee from the xorg-edgers PPA.