Gaijin Games, the developers of Bit.Trip Beat have blogged about a bug/unintentional feature in the game.

The trouble being, the game will only chooses to save progress if you get a high score. This glitch is exclusive to the US version, both the European and Japanese games were fixed before release.

If this problem is affecting you, Gaijin Games are offering two save files which you can use:

Level 1 and 2 unlocked

All levels unlocked

Instructions for use
1. Save the file to your PC and rename it "data.bin".
2. Copy the file onto your SD card in the folder \private\wii\title\WTRE
3. Insert the SD card into your Wii and navigate to the "Wii Save Data Management" screen (through the Options button).
4. Delete the BIT.TRIP BEAT save data stored on your Wii.
5. Click the SD card tab, then the "BIT.TRIP BEAT save data icon" and choose Copy.