A Strange Streak Imaged in Australia

Koyaanisqatsi writes "Today's Astronomy Picture of the Day presents a challenge worthy of a large audience: as it says, "Meteor experts don't think it's a meteor. Atmospheric scientists don't think it's lightning". An intriguing dark streak and bright flash that defies explanation showed up on some cloud monitoring pictures. The forumsetup to discuss it is currently hosed, so perhaps fellow slashdotters can shed some light over the mystery?"