Horizontal Spry menu - Problem in IE

I found this forum whilst looking for a solution for a positioning problem of a horizontal Spry menu in IE. Submenus were not displaying vertically.

Richard Williams suggestion of adding

ul.MenuBarHorizontal li ul li{
clear: left;
}

in the CSS sorted that out but the submenu is still not displaying as it should (and does in FF, Chrome, Safari and Opera).

Please take a look at the example page http://www.sougia.info/ and let me know what I should do in order for IE to display submenus of equal width. I guess that it is a question of margin or padding somewhere but I cannot get it going.

Thank you.