I have read loads of posts on this subject and I some close to the end of my tether that I am going to dump concrete5 and recommend everyone against it. I have used Joomla, Drupal and Wordpress. All install and work immediately on the same ISP.
I have tried everything that I have seen elsewhere in every combination and still can't upload files. This process is a real pig!
1. deleted the files folder, and recreated and chmod 777
2. created the /incoming/ and FTP'd a file. When I try to process the incoming it says "you must select one file" .. I did!
3. I cleared the cache
4. Made everything 777.
It typically reports the usual file permissions error,

Someone please help before I go mad!