I experienced problems with strip_tags on javascript inside <!-- //--> brackets that also contains //comments. Below is first two properly working examples, then a example to reproduce the problem. Tested in both Windows XP and Linux 2.4, both with PHP 4.1.1

$data = "<br>hello there<!-- comment // --><br>";
$out = strip_tags($data);
echo $out;
//$out = hello there, as expected :)
	
$data = "<br>hello there<!-- comment --><br>";
$out = strip_tags($data);
echo $out;
//$out = hello there, as expected :)


$data = "<!-- \n".
	"function a(i) {\n".
	"// comment\n".
	"var x=1;\n".
	"if (i>1) x=2;\n".
	"}\n".
	"// -->";
$out = strip_tags($data);
echo $out;
	
$out now is:
1) x=2;
}
// -->