Index: branches/RC/core/kernel/db/dbitem.php
===================================================================
diff -u -N -r11361 -r11362
--- branches/RC/core/kernel/db/dbitem.php	(.../dbitem.php)	(revision 11361)
+++ branches/RC/core/kernel/db/dbitem.php	(.../dbitem.php)	(revision 11362)
@@ -617,13 +617,17 @@
 			foreach($unique_fields as $unique_field)
 			{
 				// if field is not empty or if it is required - we add where condition
-				if ($this->GetDBField($unique_field) != '' || (isset($this->Fields[$unique_field]['required']) && $this->Fields[$unique_field]['required'])) {
+				if ((string)$this->GetDBField($unique_field) != '' || (isset($this->Fields[$unique_field]['required']) && $this->Fields[$unique_field]['required'])) {
 					$where[] = '`'.$unique_field.'` = '.$this->Conn->qstr( $this->GetDBField($unique_field) );
 				}
+				else {
+					// not good if we check by less fields than indicated
+					return true;
+				}
 			}
 			// This can ONLY happen if all unique fields are empty and not required.
 			// In such case we return true, because if unique field is not required there may be numerous empty values
-			if (!$where) return true;
+//			if (!$where) return true;
 
 			$sql = 'SELECT COUNT(*) FROM %s WHERE ('.implode(') AND (',$where).') AND ('.$this->IDField.' <> '.(int)$this->ID.')';