Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever Tribute Concert' at Millennium Stadium on October 8, 2011 in Cardiff, Wales. (Photo by Tim Alban/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever Tribute Concert' at Millennium Stadium on October 8, 2011 in Cardiff, Wales. (Photo by Tim Alban/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever Tribute Concert' at Millennium Stadium on October 8, 2011 in Cardiff, Wales. (Photo by Tim Alban/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever Tribute Concert' at Millennium Stadium on October 8, 2011 in Cardiff, Wales. (Photo by Tim Alban/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)

Michael Forever Tribute Concert

CARDIFF, WALES - OCTOBER 08: Christina Aguilera performs at the 'Michael Forever' concert to remember the late Michael Jackson at The Millenium Stadium on October 8, 2011 in Cardiff, United Kingdom. (Photo by Dave J Hogan/Getty Images)