Index: server/src/java/org/sakaiproject/gradebook/gwt/sakai/calculations/GradeCalculationsImpl.java
===================================================================
--- server/src/java/org/sakaiproject/gradebook/gwt/sakai/calculations/GradeCalculationsImpl.java	(revision 73899)
+++ server/src/java/org/sakaiproject/gradebook/gwt/sakai/calculations/GradeCalculationsImpl.java	(revision 73915)
@@ -770,7 +770,8 @@
 					else						
 					{						
 						// GRBK 483 - we deduct this assignment weight
-						myTotalCategoryPercent = subtract(myTotalCategoryPercent, multiply(assignmentWeight, BIG_DECIMAL_100));
+						if (!isExtraCreditItem)
+							myTotalCategoryPercent = subtract(myTotalCategoryPercent, multiply(assignmentWeight, BIG_DECIMAL_100));
 						
 						// GRBK-784 - we need a count of items in this thing. 
 						if (!isExcused(assignmentGradeRecord))
@@ -854,9 +855,9 @@
 							} else {
 								
 								// GRBK-869 : prevent division by zero
-								if(BigDecimal.ZERO.compareTo(myTotalCategoryPercent) == 0) {
+								if(BigDecimal.ZERO.compareTo(myTotalCategoryPercent) == 0 || isExtraCreditItem) {
 									
-									earnedPercentWithinCategory = multiply(BIG_DECIMAL_100, gradeRecordUnit.getPercentageScore());
+									earnedPercentWithinCategory = gradeRecordUnit.getPercentageScore();
 								}
 								else {
 									
Index: client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/panel/MultiGradeContentPanel.java
===================================================================
--- client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/panel/MultiGradeContentPanel.java	(revision 73899)
+++ client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/panel/MultiGradeContentPanel.java	(revision 73915)
@@ -1000,13 +1000,9 @@
 				}
 			});
 			searchToolBar.add(showWeightedToggleButton);
-			if(this.isShowWeightedEnabled()) {
-				showWeightedToggleButton.show();
-				showWeightedToggleButton.enable();
-			} else {
-				showWeightedToggleButton.disable();
-				showWeightedToggleButton.hide();
-			}
+			showWeightedToggleButton.disable();
+			showWeightedToggleButton.hide();
+
 		}
 		
 		/*useClassicNavigationCheckBox = new CheckBox();
@@ -1620,10 +1616,20 @@
 		isShowWeightedEnabled = enabled;
 	}
 
-	protected String getShowWeightedString() {
-		return showWeightedString;
+	public void disableShowWeightedButton() {
+		if (showWeightedToggleButton != null) {
+			showWeightedToggleButton.disable();
+			showWeightedToggleButton.hide();
+		}
 	}
 	
+	public void enableShowWeightedButton() {
+		if (showWeightedToggleButton != null && this.isShowWeightedEnabled()) {
+			showWeightedToggleButton.show();
+			showWeightedToggleButton.enable();		
+		}
+	}
+	
 	public String getSelectedSectionUid() {
 		String sectionUid = null;
 		if (sectionListBox != null) {
Index: client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/MultigradeView.java
===================================================================
--- client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/MultigradeView.java	(revision 73899)
+++ client/src/java/org/sakaiproject/gradebook/gwt/client/gxt/view/MultigradeView.java	(revision 73915)
@@ -247,6 +247,12 @@
 			Gradebook selectedGradebook = Registry.get(AppConstants.CURRENT);
 			multigrade.addGrid(selectedGradebook.getConfigurationModel(),
 					selectedGradebook.getColumns(), (ItemModel)selectedGradebook.getGradebookItemModel());
+			// GRBK-483 hide and disable the toggle button when not usable
+			if (selectedGradebook.getGradebookItemModel().getCategoryType().getDisplayName().equals("Weighted Categories") &&
+			selectedGradebook.getGradebookItemModel().getGradeType().getDisplayName().equals("Points"))
+				multigrade.enableShowWeightedButton();
+			else 
+				multigrade.disableShowWeightedButton();
 		}
 		return multigrade;
 	}