Like asclarke's post below, I'm finding this won't work at all in firefox (current version although I've been trying for multiple versions now, java stuff installed etc etc) but will work in Safari. It lists the categories and the number of links correctly but will not open the categories to reveal the links.
I'm glad that it seems to be working for some, but unless I can feel confident it works across all/most current browsers, I can't put it on my site. I really need something like this so I hope the issue can be resolved.
I did turn on the bug reporting and saw nothing showing in the source code. Suggestions gladly accepted.