This happens to me on two sites on IE and Chrome / Firefox - I copy and paste all the html including <ul id="mbmenuebul_table" class="mbmenuebul_menulist css_menu" style="width: 534px; height: 49px;">
But almost always the last menu item wraps and starts a new line and so I have to make the "width" bigger by about 20 px ( trial and error) but then I end up with excess background in the menu bar eg: top menu http://www.peachhomeloans.com.au/