Well the only Call of Duty game that I have that shows the black screen with Loading.... at the bottom is Call of Duty: Modern Warfare 3.
Now you don't say which USB Loader your using but USB Loader GX is the best it will play that game if you change the game settings to use IOS250  so if your haven't installed d2x v8.0 then install these wads.
All the other Call of Duty games play ok on the normal IOS249 setting.
Call of Duty: Black OPS
Call of Duty: Modern Warfare
Call of Duty: World At War
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