AFAIK, Nice Menus is the best 'drop-down' menu available for Drupal (short of building your own).
If you're having problems with it, I recommend looking through the issue queue (http://drupal.org/project/issues/nice_menus) for possible solutions or, failing that, posting your own message to the issue queue describing the problems you're having. Someone can then help with your problem and anyone that has that same problem in the future will also be helped.

Holly Ferree wrote: 
Hello All,

I asked a few months ago about the best Drop down menu to use and got the
answer Nice Menu's. My client and I have noticed that it has some odd
behavior about pausing and not working (especially if the menu line is not
active) and now that I actually use more than the first link now, it occurs
so much that it is an issue.

Is there a way to fix this or a better drop down menu system to use (need a
horizontal menu able to do up to 4 levels of information (I will use menu
block to split it, but still need the functionality). (please send links if
possible)
-- 
Kind regards,
Peter Anderson.
http://panda.id.au