hi i have had this for a few day and i cant seem to get it to work, i start the flight up and let it do its thing. i program the route in with sids and stars, then i put the fuel in but when i come to enter the crz FL as 180 for EGCC to EGLL, i get a message streight after entering it saying 'UNABLE CRZ ALT'. So i click clear but then my VNAV wont engage, so i take off and retract the flaps but once i have taken off i get the red overspeed bars all over the speed indicator till i touch down and they disappear, but when i am airborn and try to engage the VNAV it says 'unable next altitude', and switches to FL CH. both FD's are on all my altitudes are set in the fmc and my mcp is set to FL100ANY HELP PLEASE REALLY WANNA FLY THIS BIRD!!!!