On top of that, I found people had the same problem with the 757 III. CS team sent them a file (SimObjects\Airplanes\CS_B757-200-III_PW2037\panel/y757.tools.cab) and the problem seemed fixed. You can look up the topic (I may not copy a link in a message yet) over here:

CAPTAIN SIM FORUM › 757 Captain III › 757 Captain III - General › FSX Cargodoors cant Not open (page 2)

The fun of flying this plane is gone, due to the fact I cannot operate those doors. Please help me.