Tonights Green Day concert in Melbourne, Australia is being postponed till tomorrow due to "sudden illness". The show has been rescheduled for tomorrow night, tickets will be valid though then.

If you can't make it tomorrow, you can "seek a refund immediately from their original point of purchase."

Here's the statement from Frontier Touring.com
[quote]The Frontier Touring Company regret to advise that a sudden illness has struck down Green Day lead singer Billie-Joe Armstrong (food poisoning is suspected). Although Billie-Joe was determined to perform tonight it became apparent at 4.30pm today that he would be unable to take to the stage - particularly in light of the lengthy 2.5-3 hour show the band traditionally perform.[/quote]

Doesn't seem like anything too serious, and the show is expected tomorrow. We hope Billie is feeling better soon.