A number of the non ER 777s are fitted with the GMIS entertainment system which is non AVOD. These aircraft (18 in the fleet) although still receiving the upgraded Club World will not be able to receive an AVOD update and instead will have two different cycles of movies.
The 777s only started to receive their updates from last September and to date about 20 should have been converted. To the end of 08 the following aircraft should be converted... G-RAES, YMMP, YMMI, VIIW, VIIU, YMMH, YMMF, VIIV, YMMJ, VIIX, YMMG, YMMO, YMMN, YMMK, VIID, VIIE, VIIF and YMML!
So that makes almost half the fleet. But it will be hit and miss at present especially with the east coast routes as they use a mix of non-long range aircraft and long range aircraft which seem to be getting the upgrades first!
Hope that helps.