Sorry for the inconvenience. Known Navigation header breakage, its being "rebuilt."
There may be other unforeseen breakage primarily in the handbook portion of the wiki.
The Table Of Contents section of each "PC-BSD® Users Handbook" page may be the best workaround.
InfraRecorder is another free, open source burn application that is simple, powerful, and burns both CDs and DVDs. It uses source code from cdburnerxp, and can be portable using InfraRecorder Portable.
To burn the ISO, open InfraRecorder and click on "Write Image". Search for the location of the PC-BSD image file with its .iso extension, and double click it. Lastly, click "OK", and watch it burn.
When finished, the tray with the DVD will open and a dialog box will appear indicating that the burning process has finished.