A regression in Panther?

I found a strange thing today. With the last version of Mac OS X, if I open a menu the front application stops running. The last version of Mac OS that did this was Mac OS 9. In Jaguar I could open a menu and see an image on a web page animating, but no more. Only Quicktime movies seem unaffected.

Is it a way to speed up things and make Mac OS X snappier? Because it's true: Panther is snappier. A step backward in multithreading, a step forward in snappiness!