The root of the problem is array_merge_recursive() behavior. It processes objects like an arrays and does this in astrange way.

E.g. the following code:

class A {
	public $a = 1;
}

$a1 = new A();

$ar1 = array('key' => $a1);
$ar2 = array('key' => $a1);

var_dump($ar2);
var_dump(array_merge_recursive($ar1, $ar2));

is processed without errors and gives the following result:

In the same time

class A {
	public $a = 1;

	public function __construct() {
		$this->a = 2;
	}
}

$a1 = new A();

$ar1 = array('key' => $a1);
$ar2 = array('key' => $a1);

var_dump($ar2);
var_dump(array_merge_recursive($ar1, $ar2));

gives another result:

array_merge_recursive() has probably be replaced with array_merge or foreach (...) structure

I'm unable to reproduce this behavior; can you test with current updates,please?

I replaced array_merge_recursive with a custom recursive merge in all Zend_App classes that needed it, and I cannot reproduce the error at this point.