The 'Faith' hitmaker - who was due to perform alongside Alicia Keys at the event, which raises funds to improve the lives of families affected by AIDS - has been struck down with severe toothache after contracting an infection in his lower jaw over the weekend.
He tweeted: "Hi boyz n girls....bad news im afraid. This tooth ain't getting better in time for tonight, not enough to sing anyway..... :(
"I'm really sorry folks. You watch, it'll be totally fine by tomorrow. B****y typical. I hope not too many of my lovelies managed to grab a ticket :(. (sic)."
George - who was due to appear alongside British stars Tinie Tempah and Paloma Faith at the event at London's Roundhouse - explained earlier in the week that he resembled "a hairy football" after being struck down with the mystery ailment.
He tweeted: "On the weekend, got some kind of infection in my lower jaw and the left side of my face now resembles a hairy football. I look like Marlon Brando ( I wish....) in The Godfather if they forgot to stuff the right cheek!
"Anyway the point is I dont know if it will clear up in time for Wednesdays Black Ball Charity event with Alicia Keys which would be terrible, I don't want to let down the charity, which is excellent, and I would love to sing with Alicia, shes wonderful. (sic)"