Interesting, I noticed the threads were mostly all broken as well.
However, it looks like the site has a really smart URL auto-completion thing going on I haven't seen before.
You can mouse over the broken link and see the topic number.
Put the topic number in the URL and add a dash and forward slash.
The website autocompletes with the correct URL.
For example, broken link, first one under Guides:
Guides [Guide] Making your USB Bootable - Psychosis
If you click on it you will get:
Broken Link: http://hak5.org/forums/?showtopic=14111
Mousing over it will also show the topi