I'm reviving this ancient thread because I couldn't easily find an answer to this problem myself, so I hope this answer will help some people out.

I fixed the very slow loading of folders by adding this line:
If you look in the Samba HOWTO Collection, you'll see that the default order is host, lmhost, wins, bcast. I think the crucial thing is to have wins first. Try for yourself, hope it helps, cheers.