could be a totally diferent problem as i dont own either of those games. i have a few games that appear to black screen, (3 mins of black screen and no activity on ps3). all i can suggest is that for these games you delete all game data (not savegame) and then use multiman to get latest update and install that.
the restart the game. it will still black screen and take ages without any ps3 activity, but you will notice the actual ext hd light will be blinking. after about 3 to 5 mins the ps3 hd indicator will start flashing and then the game boots. no idea whats causing the long periods of black screen, but it isnt as long once game has been played once. although it does still do it.
i do own a call of juarez game but its the old one and it dont black screen, (at least it hasnt so far)