Ok. Now I feel like an idiot. I just discovered the clipping mask.
But that doesn't explain why changing the scale should modify the scene....

I've got a very similar situation to Paolo. Not so much the updating. I figured that out. The moment the scene gets (modified) it's no longer linked. Here is my issue. I'm bringing in a viewport. It's an interior elevation, and I've set it it already to Parallel projection in Sketchup.
In LayOut, I Insert the model. Chose the scene. The moment I set the scale it says "(Modified)".
Am I doing something wrong? All I want to do once I set the scale, is to frame the Viewport. By the way, no double clicking happening anywhere here.

i can't see any of the green 'buttons' on the scale tool. that's it. i'm done with parallels.
movin' to fusion.
and if that gives me grief, i balk at the notion of migrating everything to pc, for the sake of architecture.

Edson,
unfortunately, my file isn't even that big. but it's good to know that it's not my eyes that are failing. I'm getting the impression through the fora that fusion is more stable. I'm going to have to give that a try.
thanks for the input.
Wait. so according to the SU website, it says under the MAC hardware and software req, "Neither Boot Camp nor Parallels are supported environments." What's that supposed to mean? And why is sketchup so weird in Leopard. because that would solve this issue immediately.

i'm going to interject here hoping to get some answers. i'm running SU through parallels and i'm having the issue where the 'snap points' (if that's what you call them), and drag arrows don't show up. for example when using the tape measure tool. wouldn't think that that would be annoying but it really is comforting to see a corner light up when you're drawing a line from it.
is this an video card issue? nvidia geforce 8800gt under the hood.