How in the world did that happen ? That is really bizaare, there are people who are paying thousands of dollars trying to chase the top ten, and there you are with nothing and you have page rank of 1? ROFL
But I'd not be suprised if the domain itself of the page linking increased the weight. IE: WHT is linked everywhere, so one of it's subpages getting linked to somewhere else would have a bigger vote. It kinda makes sense with SlashDot and them since the getting linked from there can toss your PR up a bit. Just my own insight.
Google can't always spider forums - software such as vBulletin and phpbb needs to have the session IDs removed first. (vB3 does this automatically, actually.)
And every page has some PR - it's an integral part of the Google PR algorithm. But the value for any may not always show in the Google toolbar - which is a form of "simplification" of actual PR values, represented on a scale of 0-10 to measure PR according to relative values.
The whole Search Engine Optimisation (SEO) business is something that has really become common knowledge over the past couple of years. What is not common knowledge is how various SEO issues may actually apply.
Terms such as PageRank (PR) have become pretty recognisable, but is often bandied about in meaningless ways. A lot of people will chase PR without realising that PR is a tool rather than a means in itself.
I'm more worried about keyword diversity than PR to be honest. People use a lot of different ways and words for searching for the same thing. It's good to research and find which ones are more popular than others, as well as alternatives you can work into the pages.
Also from my understanding, google does not like forums and tends to give them bad PR's, therefore getting linked in a forum is bad. Especialy so if the page's keywords do not relate.