I also experienced the INVALID ENTRY error when loading flightplans into the B777. After few attempts, I tried to enter flightplans manually and found that the FMC got stuck when the route exceeds 5 pages. After 5 pages, the FMC returns INVALID ENTRY for any fix you try to enter.. Shorthaul flights with less than 5 pages of route information can be entered without problems (including from EHAM), both manually and via flightplan loading. Longhaul flights are only possible when a fix near the destination airfield is entered as last fix on the 5th page for a direct leg, or continue entering the remaining route halfway your flight... Above mainly explained my error of not being able to load flight plans.