If the import file is not a .CSV file:
1. Open the import file
2. Select File, Save as from the menu bar
3. Select Comma Separated Value (.CSV) as the file format
4. Re-import the file

If the file was saved as a .CSV file:
1. Open the import parameters and select the Fields tab
2. Ensure the fields are mapped correctly (so that the fields in the import file match the order of the fields on the fields tab)

If the Fields are set up correctly:
1. Change Regional Settings to English - USA
2. Recreate the import file
3. Re-run the import