There have been a number of instances recently where the option to download a CSV from the visitors page has resulted in an error. We have currently removed this for maintenance and we are working to get this fixed and put back up shortly.
In the meantime, to get a full comprehensive report, go to Reports>Visitor Reports Email and select the fields you want to see. To get the latest report simply click the mail icon
and you will be emailed an up to date report.