You can see in the image below an example of the above issue when using AllWebMenus DHTML Menu Maker; the Submenu of an item will appear either to the far right or the far left of the browser:
This issue occurs because the libraries of the menu that are uploaded to your server were created with an older version of the software than the menu file (the libraries of a menu are the JavaScript files that reside in our default-named awmdata folder)!
Whenever you are updating AllWebMenus you must not forget to upload to your server all the updated files - including the libraries!