LAS VEGAS -- The House of Blues at the gleaming, teeming Mandalay Bay hotel is a serious rock venue. On Thursday night, with a $32 ticket, you could have experienced a heavy metal bill that included Cannibal Corpse, In Flames, Terror and The Black Dahlia Murder.Three months ago, during another historic six-hour event, the mosh pit was fraught with much the same kind of chaos. Screaming. High-fives. And -- perhaps not coincidentally -- a copious amount of free beer.