It sounds like you might have the Energy Mode set to: low.
Go to Menu>Setup and change Energy mode to: standard.

"Energy Mode
This feature allows you to save electrical energy when the TV is off and in the standby mode. Standard mode uses more power but allows all of the background features to continue to operate. Low mode saves power (using less than 2 watts), however, using this selection will restrict or turn off many of the background features.
If the Energy Mode is set to Low the following features of the TV will be restricted or unavailable when the TV is turned off (Note: The features will operate normally when the TV is powered On):
• TV controlled recordings, including "Record Later " recordings will not be possible.
• TV Time (clock) will be lost after approximately 48 hours. The clock will need to be reset through the Time menu.
• The Timer function cannot be used to turn on the TV.
• IEEE 1394 functions that pass through the TV or IEEE 1394 recordings from the TV or Ant-DTV will not be possible.
• The amount of time required to turn on the TV will increase to more than one minute."

Mitsubishi WS-55513, Philips 55pp9352/17

Great, glad that worked.
Maybe the firmware update defaulted to low-power standby?
A 60-70 second blinking green led (DM booting) is normal anytime the tv is re-plugged in, or started from low-power standby, which is an option in User Menu>Setup>Energy Mode.
In other words, an initial blinking green led that stops, with the tv then turning on OK is normal, a constantly blinking green led that never stops is not.

Mitsubishi WS-55513, Philips 55pp9352/17