She had throat surgery a while back to remove nodules in her throat. The success of the surgery was no singing and very very light talking(almost none). I believe she is still on the road to recovery. She will have to go easy singing and work her way back slowly. Throat nodules can grow back.
Lol when I saw this question earlier I thought it would be one of the most popular because it's about Adele. Don't get me wrong, I love Adele though! :) I'm glad her voice is better and she got to sing at the Grammys last night, she was amazing.
Adele had a polyp on her vocal chords from strain and stress due to performing so much. Smoking had something to do with it as well, but now she appears to be taking better care of herself. http://FrontRowTickets.com