Just to say that this turned out to be connected to my hosting company upgrading to PHP 5.3.
As my host upgraded to php 5.3., I have the same problem that you had (using addt).
How did you manage to get rid of the error messages? (I see your page is working as supposed now)
Go here and download this batch of files and replace in your includes folder. That will update to compatibility with PHP 5.3.
I have the same problem - the web hosting has been updated to php5.3 and now my form submit is throwing an error, but the compatibilty patch has not made the slightest difference, I am still getting the following errors:
Warning: Parameter 2 to Trigger_Default_FormValidation() expected to be a reference, value given in /home/in2conf/public_html/includes/tng/tNG.class.php on line 228
Warning: Cannot modify header information - headers already sent by (output started at /home/in2conf/public_html/includes/tng/tNG.class.php:228) in/home/in2conf/public_html/includes/common/KT_functions.inc.php on line 464
Can anyone help please?