php - Unexpected character in input: '' (ASCII=92) state=1

My client says he is getting this error using my script:

Warning: Unexpected character in input: '\' (ASCII=92) state=1 in /path/to//header.php  on line 34
Parse error: syntax error, unexpected T_STRING, expecting T_CONSTANT_ENCAPSED_STRING or '(' in/path/to/header.php  on line 34

The line 34 in header.php is just use \Main\Class;

Now, I told him he has to have PHP >= 5.3.0 and he says his PHP version is 5.3.24

What could be the problem?

EDIT: The lines before and after

30. // Define absolute path
31. define("ABSPATH", $abs_path);
32. $_SESSION["abs_path"] = ABSPATH;

33. 
34. use \CNS\main\CNS;
35. $cns = new CNS();

EDIT 2:

He sent me this:

Program     Version

Apache:     2.2.24
CentOS:     CentOS release 6.4 (Final)
cPanel:     11.36.1 (build 8)
Curl:       7.12.1
MySQL       5.5.30
phpMyAdmin  3.5.5
Python:     2.6.6
Program     Version
Perl:       5.8.8
**PHP:        5.3.24**

ionCube Loader:     4.2.2
Zend Optimizer:     3.3.9
Ruby:       1.8.7
Rails:      3.2.8
OpenSSL:    1.0.0-fips