The affected area seems to be between the following locations, Ruby Hill Mine - Vault 22 - Sunset Sar's HQ - El Rey Motel - Goodsprings vicinity. Basically the entire North-Western part of the map (haven't tried South-Western part of the map past the Mojave Outpost yet). I have tried everything to check it isn't a saved game bug, from starting a new game to checking it on both patched and un-patched versions, iv'e even tried the disc on a friends xbox and even he is having the same problem on his disc (both, he managed to return the first...). The current set of quests i have to do, most need me to go to that part of the map so i'm getting really frustrated.
I guess ill just explore the Eastern part of the map for now although it's not exactly going to be fun when i keep expecting to run into the next 'no-go' area of the world map -.-
On another note, anyone know if another patch is on the way? surely these issues can be fixed, i expected the odd glitch from the GameBryo engine but this is beyond a joke now, paying full price for half a game, modern day scam.