Hi,
I once had this kind of error for couples of times, and Method told me that could be corrupted data happened in that screen, but actually, just like you, all screen are not modified at all but it just can not generate grid suddenly.
My solutions are kind of trial and error but it did the trick:
1. wait for couple of hours: it happened once to me then this screen just heal itself. Or,
2. find the master table of your screen, open it, and click "Finishing edit fields" to save it. Or
3. Copy your screen to another one, then use the new one instead.
--
Alex