A very large portion of v2 hashing is offline (btcguild - roughly 30-40%; for nearly 3 hours now) and a couple of v1 miners got lucky in a row.
The rest of the v2 network overtook them and the network reorganized.
Excuse the tinfoil hat, but, notwithstanding Eleuthria's correction of your percentages, did we just see an attempt to sabotage Bitcoin? I know Eleuthria has had the occasional DDOS before, but this particular one at this particular time? I sure hope the dev team and a few pool operators are busy combing through transaction logs with forensic attention to detail...
miss guided attempt to save Bitcoin.