well for one thing the main reason why computers freeze in carputers is temperature related or power related, seeing as it happens everytime you plug the USB drive in, im guessing your over maxing the opus power supply. You can get cigarette to USB power sources, that simply plug in. As far as the lilliput goes, How exatctly do you have it ran off your HU, and doesnt your HU have somethin like a remote ignition like an amp ? so shouldnt the monitor theraticly only work wiht the car and hu is on?
And as far as having the Lilliput shut off when you press a button, it seems like thats a shorting issue, or a grounding issue, sorry i cant be more specific im getting my first lilliput this wensday, but i'd check all the grounds around your HU, and check the ground on your switch to make sure the grounds are not close, or interfering with each other