Corrupt save file (twice)

rjj

I'm hoping that someone out there might be able to give me some advice....

I've had my Wii now for over two years and have had no significant problems. Then, about two weeks ago while playing RockBand2 I got a message about a corrupt save file. Doing some research on the net, I came to the conclusion that I was SOL, and that I basically had to start over (re-download all of my DLC, create new characters, and lose 6 months of progress in the game). I chalked it up to random chance. Now one week later, the problem has recurred. So now it doesn't seem random anymore. At no time was the power turned off, the SD card removed, or the game frozen (what individuals say are the most likely reason for a corrupt save file). As near as I can tell, the Save file for RB2 is always kept in system memory, so the SD card itself is probably not an issue.

What can the problem be?

Thanks.