When I was doing a page yesterday afternoon, I found such a problem. There is a Flash animation that has a response to the mouse.
Later, this Flash animation was completely normal when playing in the player, and then found that if the effect is only complete in a page containing this Flash animation. I have begun to doubt other code in the page.
The biggest biggest is the Marquee code that exists in the page. After removal, the page will be normal.
The conclusion is that the page itself flashes when Marquee scrolls, causing the Flash animation to conflict. This should be avoided.
If you must use two simultaneous appearances, then build an IFRAME framework in the original Marquee, which is embedded in the original Marquee, and I do this.