Christina Aguilera, always a pro singing the national anthem, couldn't make it through the Star Spangled Banner before the kickoff of Super Bowl XLV. Aguliera, who has handled the task without issue before NBA games, botched the lyrics badly halfway through the song.

Instead of "'O'er the ramparts we watched were so gallantly streaming" turned into "what so proudly we watched at the twilight's last [unintelligable lyric]."

Luckily, Aguilera had the quick, crowd-rousing "rocket's red glare" line to follow it up, which she nailed and got the packed Cowboys Stadium quickly on her side.

Still, our eyewitnesses in Dallas tell us that the crowd had some drastic reactions. "This was the biggest performance of her career and she blew it," a source with a VIP view tells me. "To mess up the lyrics was a disaster."

Another source tells us the televised roars of the crowds weren't as loud in person. "A hush fell over the stadium and everyone was looking at each other."

After the Star Spangled Banner wrapped, Aguilera headed backstage where a source tells me that the singer is "devastated." She knows she messed up big time. It's an honor to be ask and she let America and herself down. She doesn't want anyone around her. Everyone telling her she was great but she knows the truth."

Cheer up Christina. Your voice sounded as amazing as ever.

Maybe it was the pressure of the big game. After all, Aguilera got the lyrics spot on during her take on the anthem at last year's NBA Finals.