I don't have a Star Wars nick, but I might be able to help.
If what you want is http://www.domain.com/cars/ford/, is the category 'cars' and the post 'ford'? or is the category ford?
I presume you went to Permalinks under the options menu wp-admin/options-permalink.php
And if you wanted a simple /%category%/%postname%/ structure, you entered that in the custom structure. If you wanted the category to be 'ford', and everything would be listed under cars, you could just set the basename as /cars in the optional field below.
If what you're saying is you've set that and all the links return without interpreting %category% as cars, for instance, then somehow you've really buggered the WP code and I'd be curious what you may have edited. Try setting different options (such as the default for permalinks) and report what happens. A live link would help.