The blame for Ashlee Simpson's Oct. 23 Saturday Night Live lip-synching has been cast far and wide...but bad behavior starts at home. Simpson's manager dad, Joe, says the meltdown occurred because Ashlee was suffering from acid reflux that made her unable to sing without the aid of a backing vocal track (but didn't seem to prevent her from clowning brassily with host Jude Law in the opener) and her drummer forgot to reset the track after the first song. ''We're all fallible,'' Joe says. ''We put ourselves on TV and show our flaws and say, This is it, you know? Truth.'' But which part of overdubbing your daughter's voice is truthful? And why push a sick girl out for a second song that sources say SNL was prepared to cut? As for fans disappointed by an artificial ''live'' performance, Mr. Simpson insists that ''every major act in the world'' uses guide vocals, and those who don't like it ''shouldn't ever listen to the radio again.'' Okay. We're sick of ''Pieces of Me'' anyway.