Exporting works, Importing Does NOT Work At ALL with .CSV but works with errors with .ICS files!!!

I am using Sunbird_Portable_0.9_en-us.

I create a single event in a day. I select export calendar and choose .csv file format and save the file on my desktop.

then I open the .csv file in notepad++ to see that it did actually write the correct event in it then i close it without modification.

I then manually delete the event I created in Sunbird. and close Sunbird and open it again.

I then choose to import calendar(file>Import)and choose the .csv file, but nothing gets imported and my calendar remains empty with nothing imported.

Now I repeat the test as I did in the first test except i export the calendar as a .ics file.

when I import the file, it imports the events that I created except that It gives me the following error
"An error occurred when writing to the calendar Home!"

and the details of the error
"6 items were ignored since they exist in both destination calendar and C:\Documents and Settings\username\Desktop\file.ics"

why .csv importing does not work and importing .ics files works with errors.?