@is displayed with a extended attribute is set
+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.