When you get a chance check out gdiggler.thinkbling.com. It is odd that because it is a PR 3 page. and its only backlink is from a PR 2 page. Is this as odd as it appears to be?
Not a mystery, just science: http://search.msn.com/results.aspx?FORM=MSNH&srch_type=0&q=link:gdiggler.thinkbling.com
Check for the links on Google. It only has one. We all know that Google doesn't show all links. However I don't believe this is the case here. This page is such a small one and Google has never shown more than one backlink for it.
So you admit they don't show all links. Then I show you more links that ARE clearly out there (and trust me, Google can and probably has found them too) as reported by another competent SE* and you are still wondering about the PR? Good luck finding the answer to your mystery then. *add to that: 1) Bogus toolbar reporting. 2) Bogus datacentre reporting. 3) PR decimals. 4) Loads more...
Let's say that you're right. Google may have links that they aren't showing. However there might still be something to learn here. Look at the links from MSN that don't show up Google. These could be deemed as artificial or reciprocal. Maybe it's not exciting to take a look at this situation, but in such a small scenario with so few backlinks, we might be able to gain a little insight.