I am running ACF v4.4.3 (standard, not pro) and was experiencing the same issue. I tried the fix proposed by flahertydaf:
function load_field_defaults( $field ) { return $field; }
to no avail.
The problem was that I had cloned a field group, but even though the fields were given totally different names/slugs, the field values were not being saved to the DB.
Deleting the cloned group and manually recreating those fields in a new group solved the issue.
