z-indexed layers and Flash movies

Hallo,

I have a navbar which displays dynamic menus when mouse hovers its items.

In the page I have positioned some swf Flash files, and now the displayed
menus are covered by the Flash movie, even if I played on the z-index.

Is it possible that Flash movies force the z-index not to work, or do I have
only to find the right solution?

Thanking you in advance,

Best Regards,

Pietro