This happened to my best friend last night and pointed me to this link when he did some research. Just passing it along.
Originally posted by ArticleUnfortunately, gamers eager to sample the cel-shaded beat-'em-up were in for a very nasty surprise. That's because the demo contained a glitch that will erase all saved games on the memory card or cards currently inserted in the console.
Retail (Tuesday) • Just Dance 4 Rock Band 3 DLC (Tuesday; * has optional Pro Guitar/Bass for an extra $1) • A Flock of Seagulls – I Ran (So Far Away) • Billy Squier – The Stroke * • Billy Squier – Everybody Wants You