Actual Cost value =0 after a scheduling ?????

Hi Guys

I’ve chosen into Autocost Rules that Actual COst will be calculated based on Budgeted Cost and % complete.
When I type % Actual Cost is immediatly calculated but as soon as I make a F9, the value goes to 0.
What is strange is that event does not affect all activities, only for some...
Anyway, I must type actual cost value.

My schedule has been crashed 2 days ago after a bloody crash on our network...