Support Non market app installation does not work

view story

http://androidforums.com – I recently bought an LG Motion from Metro. It was working fine I could install non-market apps until it received the update. Not sure if the update does not allow non-market installations because I know that the check mark in security for non - market apps is ticked. PS. I can get to the install app screens, but the install button does not do anything it stays solid, the only functional button is the cancel button. (General)