It's the javascript. The treeview script doesn't have a hover function.
You could try having a play with the DDR menu download near the bottom of this page:
https://nbstore.codeplex.com/releases/view/34143
I haven't tried it so can't help with it.
And there is also the 3rd party menu module here:
http://store.dnnsoftware.com/home/product-details/navigation-suite-all-in-one-v10454-mega-menu-system-4-premium-xhtml-skin-packs-w3c
That has many variations and a provider for the store.
Regards
ROb
You could try having a play with the DDR menu download near the bottom of this page:
https://nbstore.codeplex.com/releases/view/34143
I haven't tried it so can't help with it.
And there is also the 3rd party menu module here:
http://store.dnnsoftware.com/home/product-details/navigation-suite-all-in-one-v10454-mega-menu-system-4-premium-xhtml-skin-packs-w3c
That has many variations and a provider for the store.
Regards
ROb