How did you go about confirming that the fields were all integer fields? If either Member or NonMem were a text field, you would get the results you describe. Those are the only fields that could single handedly be responsible. If other fields, in addition to those, were also text, you would also get those results.
You need to have a blank line prior to the indented text. I added it for you.
I wonder if perhaps you somehow accidentally created variables with the same names, and the variables contained text. That would account for all of the symptoms, including the fact that it worked when re-opened (since the variables would no longer exist).