parsing - PHP Parse error: syntax error, unexpected T_STRING, expecting T_FUNCTION

I get this error in my PHP code:

PHP Parse error: syntax error, unexpected T_STRING, expecting T_FUNCTION in C:\Inetpub\wwwroot\webroot\www.novotempo.org.br\lib\Twitter.php on line 54

The line in question:

define('DEBUG',false);

Searching the net I found that this usually occurs when you´re using PHP 4.xx, but I´m using 5.2.6 (Just checked it using phpinfo()).

I tried locally, and in two other external hosts, but it keeps returning the same message.

Why does this happen? How can I fix it?