Are your CSS Menu's submenus disappearing in Internet Explorer 7 and Opera?
If your CSS Menus don't have a background color or image and you have a graphic item behind them then it's possible that IE7 and Opera users are having a hard time accessing your submenus. To get round this follow these steps:
Download and unpack the file attached to this article
Select you CSS Menus item
In the Actions palette check Background if it isn't already checked
Check Use Image for each option that doesn't already have a color or image applied to it
In each Image field that doesn't already contain an image select the _transparent.gif file that you downloaded in step 1