Can you give more details on what you did. For example did you have a .htaccess file before and if yes, was it empty? If you did not have one in the first place did you try to delete it and restart your server again? Which OS and version are you running? etc
Have you tried removing the .htaccess file and the error goes away? Could you possibly post a copy of the contents of the .htaccess here so we may take a look at it please.