I know this is a little old, but, I implemented a very cheesy solution for it – I noticed if you scrolled the screen even on pixel, the menu problem cleared up. So…
In header.php
modify this:
<div id="grid-container" >
To this instead:
<div id="grid-container" onLoad="setTimeout('window.scrollTo(0,1);', 1000);setTimeout('window.scrollTo(0,0);', 1000);">
It just “bumps” the screen one pixel after the whole shebang is loaded. Cheesy as hell, but it works for the moment (and the 5 minutes I had available for a fix ?? )