10.04.2008 15:01:20:[1001][E] Unable to copy file to FTP: "xxx.xxx.xxx.xxx" [Requested action not taken, file not found or no access.]
10.04.2008 15:01:20:[1001][E] Unexpected error. Either source or archive folders are invalid[Unable to copy file to FTP: "xxx.xxx.xxx.xxx" [Requested action not taken, file not found or no access.]]
The 550 error is a message from the server stating that the account you have currently logged in as does not have permission to perform the action you are attempting.
APBackup creates archive folder then upload files to this folder. So check your account rigts to CREATE folders and files in the destination folder.