The following are invalid rows in the import file

Hi 

I am trying to add import enrollees to a training course in Adobe Connect. I have created an excel file with headings (in separate columns) of:

first-name last-name login email password

I then enter a couple of entries and then save as a CSV file. When I import into Adobe Connect I get the following message:

The following are invalid rows in the import file

and then a list of the entries. What am I doing wrong?!