diff -uNrp zabbix-1.8.6.orig/frontends/php/include/forms.inc.php zabbix-1.8.6/frontends/php/include/forms.inc.php
--- zabbix-1.8.6.orig/frontends/php/include/forms.inc.php	2011-08-12 01:33:40.000000000 +0900
+++ zabbix-1.8.6/frontends/php/include/forms.inc.php	2011-08-15 01:38:21.000000000 +0900
@@ -1929,15 +1929,13 @@ ITEM_TYPE_CALCULATED $key = ''; $params 
 			$mcb = new CCheckBox('multiplier', $multiplier == 1 ? 'yes':'no');
 			$mcb->setAttribute('disabled', 'disabled');
 			$mltpbox[] = $mcb;
-			if($multiplier){
-				$mltpbox[] = SPACE;
-				$ctb = new CTextBox('formula', $formula, 10, 1);
-				$ctb->setAttribute('style', 'text-align: right;');
-				$mltpbox[] = $ctb;
-			}
-			else{
-				$frmItem->addVar('formula', $formula);
+			$mltpbox[] = SPACE;
+			$ctb = new CTextBox('formula', $formula, 10, 1);
+			$ctb->setAttribute('style', 'text-align: right;');
+			if(!$multiplier){
+				$ctb->setEnabled('no');
 			}
+			$mltpbox[] = $ctb;
 		}
 		else{
 			$mltpbox[] = new CCheckBox('multiplier',$multiplier == 1 ? 'yes':'no', 'var editbx = document.getElementById(\'formula\'); if(editbx) editbx.disabled = !this.checked;', 1);