Problems with Better Extended Live Archives

I’ve begun to use the plugin Better Extended Live Archives on my blog and it works fine up to now.

But I would like to improve my usage a bit, and I don’t get the expected results:

– I want to use hierarchical categories, with the upper level acting only as “supra-categories” and containing no posts; these categories are displayed on the Archives page with (0) post, but the link is active and when clicked return a message such as “Could not open cache file ‘cat-51.dat'”. Any way I can improve this?

– I already use the 3 tabs provided for categories, dates and tags. But now, I would like to add a custom hierarchical taxonomy, possibly with another tab working on the same pattern as the categories one. How can I achieve this?

Thanks for helping.