Some time around 7:30 PM, the roof of the main stage caught on fire–no word yet on why and how, but here's a photo just as it was getting put out. Crisis averted!
EDIT, 9:32 P.M.: We're hearing via Twitter it was both on purpose and a mistake during Coheed and Cambria's set. We'll let you know for sure when we find out!
EDIT, 1:02 A.M.: Looks like it was an accident after all–a lighting instrument caused the roof to catch on fire. Solved!