This error was driving me nuts.

Error in Apache Log:
[error] [client 127.0.0.1] WordPress database error Table ‘wp_categories’ doesn’t exist for query SELECT cat_name FROM wp_categories WHERE category_nicename = ‘12′ made by require, require_once, include, get_header, locate_template, load_template, require_once, breadcrumbs, referer:

I edited the core files to no end.  Of course the last thing I checked after four to five hours of hacking was the breadcrumb plugin by Daniel R Naylor.  Because I was sending custom URL Params it was trying to grab the category out of a depecrated table.

FIX: Either use another breadrumb if your going to be using custom URL Parameters or edit the current one.
– comment out this entire elseif statment:
elseif ( !empty($category_name)

That keeps it from looking for that table and will end the errors.