When you make hand coded updates to large code chunks at the bottom of the code chunk dreamweaver gets confused when trying to identify the code.
On this page you hand coded line 117 instead of updating it in the server behavior directly.
This line:
$InsertGoTo = "send_email_appt_set.php?ID=[InsertID]&altEmail=" .((isset($_POST["alt_email"]))?$_POST["alt_email"]:"") ."&companyID=" . $_POST["company"] ."&altEmail2=" . $_POST["alt_email2"] ."&altEmail3=" . $_POST["alt_email3"] ."&altEmail4=" . $_POST["alt_email4"] ."&altEmail5=" . $_POST["alt_email5"] ."&altEmail6=" . $_POST["alt_email6"] ."&altEmail7=" . $_POST["alt_email7"] ."&altEmail8=" . $_POST["alt_email8"] ."&altEmail9=" . $_POST["alt_email9"];
would have looked like this had you used the interface:
$InsertGoTo = "send_email_appt_set.php?ID=[InsertID]&altEmail=" .((isset($_POST["alt_email"]))?$_POST["alt_email"]:"") ."&companyID=" . $_POST["company"] ."&altEmail2=" . $_POST["alt_email2"] ."&altEmail3=" . $_POST["alt_email3"] ."&altEmail4=" . $_POST["alt_email4"] ."&altEmail5=" . $_POST["alt_email5"] ."&altEmail6=" . $_POST["alt_email6"] ."&altEmail7=" . $_POST["alt_email7"] ."&altEmail8=" . $_POST["alt_email8"] ."&altEmail9=" . $_POST["alt_email9"] ."";
I've updated it to the latter and the page opens properly again.