This shapefile represents the counties of NM. I am trying to compute the area of each polygon (yes, I know there is an area field, but this is a simpler example of a problem I'm having which doesn't have the areas). I load the shapefile into qgis and set the projection to UTM 13 NAD 83. I open the attribute table, enable editing, open the field calculator, select new field, real number, 20 digits, 4 digits precision, and set the expression to $area. Of the 33 counties, all but 3 show an area of 0. The 3 with non-zero values have values that bear no relationship to the actual area. I also tried reprojecting the shapefile to Conus Albers, open that in a project with the Conus Albers CRS, and get the same result. Obviously I'm doing something very wrong, but I'm not seeing it.
qgis 2.02 64 bit Windows 7 Pro, 64 bit