Update to 4.2.2 blew up my board.

[CarlitoBrigante]

And for forum owners, a possible solution to this is just to change this in includes/class_core.php line 5733

      		if (error_reporting() OR ini_get('display_errors'))
      		{
      			if (defined('DIR'))
      			{
      				require_once(DIR . '/includes/functions_log_error.php');
      				$message = "Warning: $errstr in $errfile on line $errline";
      				log_vbulletin_error($message, 'php');
      			}

to this

      		if (error_reporting() OR ini_get('display_errors'))
      		{
      			if (defined('DIR'))
      			{
      				require_once(DIR . '/includes/functions_log_error.php');
      				$message = "Warning: $errstr in $errfile on line $errline";
      				log_vbulletin_error($message, 'php');
                                if(!ini_get('display_errors')) return;
      			}

This is a very rushed out solution, and I encourage you guys to double check it as I really really do not have the time (do not want to be mean, I just have been up in front of the monitor for 18 hours straight upgrading stuff already).

--------------- Added [DATE]1381371455[/DATE] at [TIME]1381371455[/TIME] ---------------

Guys, I can confirm I had a similar problem with attachments in a forum and it was, once again, caused by the issue I posted above about warnings coming out at the head of the AJAX response. Using the fix above and hiding the display errors made them work for me.

Not sure this covers also your cases (it does not seem to as some of you are reporting issues with fresh installs which should not contain deprecated messages), but just double check this is not what is causing the problem for you as well.