There shouldn't be any problems with the number of items in a menu (but obviously, millions would cause a problem with any system - which isn't the case here).

One thing I always suggest after code validation is to remove external javascripts not related to udm4 and see if the problem goes away. There as times when event handlers or other javascript code conflicts with the udm code.

Another option may be to use the CSS version by checking out these links:

http://www.udm4.com/demos/other-purecss.php
http://www.udm4.com/manual/developme...t-css-cssmenus

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