In report design view, select one of the labels that has this problem. You want to check a couple of things.
The .ForeColor and .BackColor of that label cannot be the same color.
The label's .Visible property must be True
The label should be "in front" of the detail background.
The label's .Caption should not be empty.
No code underlying the report should directly address the label's properties related to visibility.
You should also make sure that you actually have data (or that you don't have a NoData event firing off to intercept the page.)