Thursday is a busy day for pop acts on TV talk shows. Before that though, look for Avril Lavigne on the Late Show with David Letterman on Tuesday. She’ll be on Live with Regis and Kelly on Wednesday as well. Then on Thursday, look for Kelly Clarkson on Regis and Kelly — if her vocal problems aren’t as serious as some fear anyways. Later that night, Michelle Branch performs on the Tonight Show with Jay Leno, followed by *NSYNC star Joey Fatone on Last Call with Carson Daly.