What the fuck, Nintendo, indeed.
Nintendo says that the bug, which renders players unable to advance, occurs if players obtain the Ice Beam and then backtrack after defeating the "two-legged spiked enemy" instead of opening the next door. The company says that proceeding forward after the battle should prevent the glitch from occuring.
Besides an apology and tips for avoiding the glitch, Nintendo is also offering to repair saved game data for those players who are stuck. However, the fix requires that you physically send your save data to the company in the mail. Players in Japan may copy the data to an SD card or send the entire Wii to the following address: