Navigation Links: undefined method `full_name' for nil:NilClass

Hi, I just started with basic Rails app yesterday, I'm stucked in the Navigation Links part of Costumizing Form. I've been following up the videos step by step, I re-watch them all (untill this part) twice.

At min 3:03 when Jim adds the link using "current_user.full_name" is where I get this error.

undefined method `full_name' for nil:NilClass

Extracted source (around line #19):

16:           <li><%= link_to "All Statuses", statuses_path %></li>
17:         </ul>
18:         <ul class="nav pull-right">
19:           <li><%= link_to current_user.full_name, edit_user_registration_path %></li>
20:         </ul>
21:       </div>
22:     </div>

Edit 1: It's fixed. I really didn't do anything, I went to sleep, then start to work on the project again, run the rails server and voila!

Edit 2: Using Chrome it runs like a charm, no error. But I started this project using Firefox's Nightly (Just to live on the edge as a "Pro Dev") and this is where the error occours.

Any way to fix this? or I just continue the develpment on Chrome?