removing zero value in cells

In a table I've created, once the first value is entered, the remaining cells that would have a value based on a simple sum formula all of a sudden have a zero.

That's fine, but once additional information is entered, the zero value doesn't go away so the resulting sum value is overlaying on top of the "0"!! Has anyone else seen this? I've tried numerous steps, and short of rebuilding the template from scratch, not sure what to do. Any help appreciated.