Nothing in Start and End Date SmartColumns

Answer:

It's possible you are using symbols which are defined as something other than "normal" symbols.  For example, if your start symbol is defined as a baseline symbol, the date won't be displayed in a Start Date SmartColumn.  It would, however be displayed in the Baseline Start Date SmartColumn.  Resolving your dilemma may be as easy as changing the symbol to a normal symbol in the toolbox.