I'll throw my 2 cents here, i think Fisher hit the spot, and the big problem are the new users (most of them, not all):
1 - Not much information (logs or other stuff) regarding the problem in hand
2 - Explanation of the problem itself is of bad quality
3 - Most posts itself are written in bad English
4 - New users don't vote answers as correct
5 - They don't search before asking
This removes motivation for others users to answer those questions, resulting in an high percentage of unanswered questions.
I use Ubuntu, but i also use Slackware (and used other distros in the past) like so, i've been participating on other helping sites, like linuxquestions or arch forums and such, and they have a different philosophy:
Users should be educated on first searching then asking finally voting
In here, they don't bother searching before, they just ask, and we can see this site has a lot of information already, most of the questions asked, have already a solution and has been asked before.
So, how to lower the unanswered questions?
As a new user joins AU, he should receive a warning or some basic instructions, like:
Search -> Ask -> Vote
1 - Search first, 2 - Ask only if your question isn't found 3 - If answer is given mark the question as answered
When a user doesn't do this, the question should be closed and the reason why is the above instructions.