I've tested the menu in IE7 & IE8, the menu works fine but I noticed 2 minor issues, and the client's experience might have something to do with the first one.
- From your homepage, if you click "Special Diets" it will take you to the page (/menu/MKMeals.html) wish the list of MKMeals.
While all the other pages seems to have an invalid link for the "Special Diets" link, clicking it doesn't go anywhere and its href="#url".
Althought it doesn't break the menu on my IE8, the invalid URL might be causing some issues with the Client's browser, you can ask to click the link from the homepage and check if they would encounter the same problem.
- On the page senior-food-gifts.html, the image preload is throwing a JavaScript Error (MM_preloadImages is not defined), in some cases a JavaScript error could disable other JavaScripts from running, so I'd check all pages and correct any similar JS errors.
Hope this helps