Why is this page a PR 3?

Hi everybody!

There's a question that has been troubling me. I have a site with PR 5 at index page and rest other pages that have got links at all pages have a PR 4 consistently. However, one single page, which has also got links at all other pages, is just PR 3. All I know about PR is that more the links to a page, more the PR. Also, the number of links to all my pages with PR 4 at linking pages are uniform. Can someone shed some light? Here's the page-

http://www.mywebastrologer.com/freeques.asp

Another interesting thing is that when right-clicked the page and clicked on 'Backward Links', it just showed me 2 backlinks, while in fact there are over 25 PR 4 pages that link to this page (all sub-pages of the site). Why are they not showing?

Why I'm concerned is also because I'm trying to optimize the page for 'Astrological Advice' and so I'm linking to it internally with that link text. Less PR might indicate that all the link text that I've used is not being factored in and that could be a problem. Help please!