Extended Menu itself is completely browser independent. If you report any problems it is important to mention which menu template or CSS you are having problems with and which modifications you made.
Please report problems in a forum (assuming you have searched the forum already). The suckerfish menu templates are all based on a independent source (link is provided next to each of the menu templates). Problems may likely appear with the original implementation as well and you may not want to restrict your search to the Extended Menu.