mega menu

I’m trying to convert a site with a huge navigation structure to wordpress. (Its at http://www.artunframed.com)

It needs an alphabetical list of artists

I tried using a mega menu but after 60 or 70 artists, the menu was corrupted and deleted many of the entries.

I’ve read that wordpress has problems handling a large menu.

Is wp 3.5 an improvement or if not, do you have any suggestions?

Thanks