As stated by Markoz on how to get this going already.....
Just make sure do all the uninstall, removal from Add program and by doing search for any CS777* on your system folders.
Install the 1.2 and reboot your PC.
Then run FSX with some sort of default twin turbo prop as your starting flight. Do not select that twin prop plane and fly now. You need to select the B777 you want to fly and then click fly now.
When you select the 777, launch FSX and you see the B777 sitting on the runway.....Do not select another 777 because you change your mind and want to fly another livery instead.
You need to exit out and do the start up process again by selecting the livery you want to fly this time.
Once you got this routine square away with your B777 all running good ready for take off (no pending message on EICAS), then install the rest of your add-ons like the 300ER and the Freighter version. After you install all these...reboot your PC again.

Kin M.
(Klax)