It's not really a huge bug, but if, let's say, you're updating your profile (changing info, etc.) and then click on the Forums link, instead of showing a drop down menu, it takes you to the page where all forums are listed.
Just tried it on hover nothing shows. There's an arrow-down thing next to Forums but nothing happens. I also tried Tools and Marketplace, nothing shows either. I am using Chrome on my laptop. Maybe it's a Chrome thing.
It works on search results... it's just different based on the active tab. If the "Forums" tab is inactive, then it's just a small sub-navigation drop-down... the big list of all the forums is only available when you are in the forums (Forums tab active).