I'm as familiar as anyone else that I'll be able to find, but I've really got no way to explain why the window isn't becoming visible.

Is it possible that it's trying to default to the process's nShowCmd value instead of a constant "normal" window size? That would seem most likely - nearly every issue we've had along these lines in the past have been some form of inherited process-wide setting.

The other possibility is if the screen size is so small that the window is being put outside of the bounds, and then the visibility test being used is one that checks whether its bounds are within the current monitor. That may also get a false negative in some non-interactive cases.

(I'm assuming, based on two examples, that they're all timing out at the "wait_visibility" call.)