qgis - After re-open of old project file, several layer selections no longer available

I'm new to QGIS.

I created a QGIS project, loaded 1 to 3 shapefiles via Add Vector Layer (from 2008 TIGER/Line Shapefiles http://www2.census.gov/cgi-bin/shapefiles/state-files). The maps look fine and I can interact with them.

Under Layer many of the "middle" options are available after loading the shapefile, e.g., Open Attribute Table, Toggle Editing, Save as ..., Properties.

I then save the project.

After closing QGIS and re-opening the project file, all of the layer options mentioned above (and a few others) are now greyed out and unavailable.

Are these options only available right after loading a shapefile? What good is a project file if one cannot interact with data saved with the project?

And why are the Edit options always greyed out and not available?

What am I missing?

Thanks for helping me understand QGIS.