Nintendo acknowledges game-breaking Zelda bug

Nintendo has acknowledged the existence of a game-breaking bug in The Legend Of Zelda: Skyward Sword.
According to Zelda Informer, the company has acknowledged that completing parts of the Song Of The Hero quest in a certain order means the other parts don't trigger as normal.
"We have been made aware of the issue that results in being unable to progress in the Song Of The Hero quest," reads an email Nintendo is sending to users who have notified them of the bug. "If the game has been saved after completing the sequence of events, it will no longer be possible to proceed through the game on that save file.
"The only options at that point are to either start the game over or to use an earlier save file to continue. The situation is caused by performing the following sequence of events:

• At the beginning of the quest, go to Lanayru Desert to retrieve the song of the Thunder Dragon.
• In the Lanayru Mine, speak with Golo The Goron.
• Complete the Thunder Dragon's event, and receive his song.
• Before heading to the forest or volcano regions, speaking with Golo in the mine again.
• At this point, the forest and volcano events will no longer occur, making it impossible to continue."

There's no other fix available - you'll just have to make sure you complete the quest in a different order, or use multiple save files. Nintendo does, however, say it is "documenting all feedback."
Source: Zelda Informer