TopMenu - conflict with Google AdSense?

[allpar]

I am using TopMenu (the first one, I think) at allpar.com (all inner pages, not the front page). It works great - but in testing, I didn't notice that, when using Safari, it seems to "drop" the submenus as soon as you mouse over a Google AdSense link. Is there any way to fix that?

Sample: http://www.allpar.com/history/ (cars drops down).