go to "settings" then "security & lock screen". Third option from the *bottom* is "clear credentials". Hit that. Then remove your lock.
I got usb tether to work with foxfi by the way (but only after successfully installing motorola ADB interface drivers). I read that you can then have your laptop share the connection wirelessly via the pdanet windows app, but haven't tried that. (for usb tether, you don't need the security certificat/phone lock)