Ok...the directory you submit to is a pr5,or whatever. The category page is a pr0. What is the actual value of the backlink pr5 or pr0?
As long as the link get's indexed it can help you rank, pr doesn't matter, it's just that the PR is a good indicator of quality, SEO is about getting votes and getting search phrase text links.
if the domian in a expired pr5 domain, then probably you won't get much benifit. but then a genuine pr5 website will have the inner categories well ranked! so don't worry too much about it! if the rank is 0, then it will catch higher ranks with time!!
The actual value of the backlink is from the page you're listed on divided by the number of links on the page. Just because the toolbar displays PR0 it doesn't necessarily mean the PR value equals 0.
It's value will be PR0 of course. Anyway - I suggest to pick only best directories, you will loose your time to put everything everywhere...
No need to worry bout that, votes and backlinks matter for SE's but I will suggest you to put your link in good directories in revelant cat. Only backlinks from high PR revelant sites will help you to get good rankings