How can you roll-over a menu in an iPad? I'll admit I'm an iPad noob, but I grabbed my wife's and tried to reproduce the issue. I'll be darned if I can't figure out how to roll over the top level and see the second level at all... oh I see... you just click on it ;)
I can't reproduce the problem on an iPad. It appears to work correctly. This must be an issue with the iPhone browser or the css you have added for the iPhone.