Accessing objects within MovieClips

I’d like to use instance names to access movie clips that are inside other movie clips, which may be inside other movie clips, etc. Everything works fine until things start moving, and then instance names become weird…

Sometimes, I can access the instance name, but tracing the position reveals that it isn’t moving (even though I can see it moving on the screen!)

Sometimes, I can’t even access the instance name, and even getChildByName returns null.

It’s been driving me crazy for days now… Could anyone shed some light on this issue, what’s going on???

Thanks a lot!
Emil