Bukkit/CraftBukkit — comment on commit 4d220e5d09174d2dfbfb8cff94b0edd10bbbc7b2
File:  line 0
By KaneHart:

This seems to be a common issue with the bukkit version if you go to the end first time you fall (like no world got generated yet) or finish it and use the portal you go back to the main world but yet again no terrain seems to generate or just load period where my bed was and fall through again)