I think he means a severe and rapid implosion of the economy due to a systemic meltdown of the banking system. Basically this scenario is off the table since March.Quote from Susannah:
Bernanke: Danger of downturn appears to have faded
http://biz.yahoo.com/ap/080609/bernanke.html
Doesn't mean the economy won't be soft for a long time to come.