Index: trunk/kernel/admin_templates/incs/grid.js
===================================================================
diff -u -r5022 -r5031
--- trunk/kernel/admin_templates/incs/grid.js	(.../grid.js)	(revision 5022)
+++ trunk/kernel/admin_templates/incs/grid.js	(.../grid.js)	(revision 5031)
@@ -7,19 +7,29 @@
 
 GridManager.prototype.AddAlternativeGrid = function ($source_grid, $destination_grid, $reciprocal) 
 {
+	if ($source_grid == $destination_grid) {
+		return false;
+	}
+	
 	if (typeof(this.AlternativeGrids[$source_grid]) == 'undefined') {
-		// create array if it is first alternative grid to this one
+		// alternative grids not found, create empty list
 		this.AlternativeGrids[$source_grid] = new Array();
 	}
-	this.AlternativeGrids[$source_grid].push($destination_grid);
 	
+	if (!in_array($destination_grid, this.AlternativeGrids[$source_grid])) {
+		// alternative grids found, check if not added already
+		this.AlternativeGrids[$source_grid].push($destination_grid);
+	}
+	
 	if ($reciprocal) {
 		this.AddAlternativeGrid($destination_grid, $source_grid);
 	}
 }
 
 GridManager.prototype.ClearAlternativeGridsSelection = function ($source_prefix)
 {
+	if (!this.AlternativeGrids[$source_prefix]) return false;
+	
 	var $i = 0;
 	while ($i < this.AlternativeGrids[$source_prefix].length) {
 		this.Grids[ this.AlternativeGrids[$source_prefix][$i] ].ClearSelection();