There is a typo to the Crusaders' Pinnacle flight steps in the Icecrown guide (both Factions) that prevents the guide from loading. The following steps will get it fixed for you until we get it fixed with an update.
1. Navigate to your WoW/Interface/AddOns/ZygorGuidesViewer/Guides folder and open up the ZygorLevelingAllianceWOTLK.lua (or Horde version depending on which one you are using) with your favorite text editor
2. Search for: Crusader's Pinnacle
3. Replace with: Crusaders' Pinnacle
4. Repeat 2 & 3 until all are changed
5. Save the file
1. Navigate to your WoW/Interface/AddOns/ZygorGuidesViewer/Guides folder and open up the ZygorLevelingAllianceWOTLK.lua (or Horde version depending on which one you are using) with your favorite text editor
2. Search for: Crusader's Pinnacle
3. Replace with: Crusaders' Pinnacle
4. Repeat 2 & 3 until all are changed
5. Save the file