I was having some problems yesterday trying to import some xy (latitude and longitude) points into QGIS using the Delimited Text plugin. It turns out that a) my Excel spreadsheet should have been exported as “Windows Comma Separated” rather than the default (Mac) “Comma Separated Values,” and b) the last column in the file MUST have values the whole way down in order for the plugin to determine the number of columns (and therefore, apparently, which column has the x and y values). I was being lazy and hadn’t input all the zero values that should have gone in; now I probably should go back and do that.
Hopefully this will help someone else.
P.S. If you’d like to fill in all the empty cells, you can follow these directions. You can just copy and paste into the selection, rather than doing the formula thing.