The above link is the exact steps to load a .CSV into outlook.

I would check the .CSV you are currently attempting to up load and double check it doesn't have any custom fields or if some of the columns have improper values. Even an empty cell above the the column can cause your error.

Please keep us update on what values you are importing ( I.E names address appointments) you maybe also adding in appointments that you are not the owner of or dont have the proper delegate permissions.This will also keep you from loading the .CSV.

Keep us posted