While driving my 08 FEH (82K miles) in local traffic the other day going about 15-20 mpg as I had just crossed thru an intersection and I got the infamous triangle and exclamation point, along with the "Stop safely now" message.
The gas engine seemed to have stopped but I still had power from the electric battery/motor, so I was able to drive it about 1/2 mile until I could safely pull over and turn it off. I was able to restart it and everything seemed to work fine. I drove it to the Ford dealer for them to investigate what the issue may be.
So far they haven't found anything obvious, but they did call me to let me know they believe its a problem with the electronic throttle body control ($494). - Unfortunately this is not covered under my extended powertrain warranty. : (
Hopefully this new throttle body part will fix this problem. Although from what I've read here so far, it appears this could be due to a number of differing causes? -Keeping my fingers crossed.