Nintendo has acknowledged the existence of a game-breaking bug in Zelda: Skyward Sword and offered a workaround.
According to an email sent to affected players and reprinted on Zelda Informer, the issue results in being unable to progress in the Song of the Hero quest.
If the game has been saved after completing a certain sequence of events, it will no longer be possible to proceed using that save file, meaning players have to start over or revert to an earlier save to continue.
The situation is caused by performing the following sequence of events during the Song of the Hero quest. Beware of spoilers:
1. At the beginning of the quest, go to Lanayru Desert to retrieve the song of the Thunder Dragon.
2. In the Lanayru Mine, speak with Golo the Goron.
3. Complete the Thunder Dragon's event, and receive his song.
4. Before heading to the forest or volcano regions, speak with Golo in the mine again.
5. At this point, the forest and volcano events will no longer occur, making it impossible to continue.
This issue WILL NOT OCCUR if the Fire and Water Dragon songs have already been collected before collecting the Thunder Dragon's song. Talking to Golo in the Lanayru Caves will also NOT trigger this issue.
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.
I wish I had a better answer, but I'm afraid there currently is no other fix available. I can assure, however, that we are documenting all feedback we receive on this issue. Thank you for your patience and support.
Skyward Sword is "rule-breaking, dream-weaving, tech-loving, heart-soaring stuff", according to our 9.8/10 Legend of Zelda: Skyward Sword Review.