from http://kiddynamitesworld.com/the-cme-margin-notice-that-has-everyone-in-a-tizzy

EDIT – the CME has released a clarification. In part:

“Yesterday, CME Group successfully transferred MF Global customer positions to a new clearing member with part, but not all, of their funds, as approved by the bankruptcy trustee and the court. By reducing the initial margin “ratio” to 1.00, we ensure that margin calls that are issued to these transferred MF Global customers will be limited to bringing their accounts into compliance with the lower, “maintenance” margin levels. Maintenance margins are set to provide appropriate risk management coverage. Initial margins are set to provide an additional buffer against future losses in the account.”

Apparently we have a reduction in initial margin level rather than an increase in maintenance margin level.