[Typo3] sporadic:Call to a member function on a non-object

[Nikolas Hagelstein]

hi,
One of my extensions throws the the following error sporadically:
Fatal error: Call to a member function on a non-object 
in xxxxx/class.tx_hnks_pi1.php on line 50

Line 50 belongs to main and says: 
$GLOBALS['LANG']->includeLLFile('EXT:hn_ks/locallang_db.php');


Sporadically means on some clients it happens sometimes
and on other it happens never.

?!? any ideas?

bye,
		Nikolas