Losing changes in World Editor

I gotta figure this is a noob mistake i'm making, so I apologize up front.

I'm having a general problem where I try to move objects around in the World editor and then when I switch editor modes, I lose my changes.

Here's how to recreate the problem:

1. Start the FPS Starter kit demo.
2. Start a mission.
3. Press Alt-C.
4. Press F11
5. Press F4.
6. Place a trigger. (Mission Objects->Mission->Trigger).
7. Click somewhere on landscape to deselect the trigger.
8. Click on the trigger to re-select it.
9. Move the trigger.
10. Press F11.
11. Press F11 again.
12. The trigger moves back to the original location.

I find if I select another object before pressing F11, I dont' lose my changes.

Can somebody explain why this is happening? I sense I'm missing something fundamental about how this editor works.

Thanks,
Mike