• The @ is displayed with a extended attribute is set
  • The + is displayed for an ACL.
  • IF you have both an attribute and a ACL then you see @.

Run the command ls -le filename to see if it has any ACLs set.

Since your problem seems to be with accessing the file, I bet you have a ACL set in addition to an extended attribute.

To get rid of an ACL run echo | sudo chmod -E filename for a file or echo | sudo chmod -R -E directory name for a directory.