Index: src/org/eclipse/jface/viewers/deferred/ConcurrentTableUpdator.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jface/src/org/eclipse/jface/viewers/deferred/ConcurrentTableUpdator.java,v
retrieving revision 1.8
diff -u -r1.8 ConcurrentTableUpdator.java
--- src/org/eclipse/jface/viewers/deferred/ConcurrentTableUpdator.java	13 Nov 2006 04:44:59 -0000	1.8
+++ src/org/eclipse/jface/viewers/deferred/ConcurrentTableUpdator.java	16 Apr 2010 12:12:12 -0000
@@ -282,8 +282,8 @@
      * @param includeIndex the index that should be included in the visible range.
      */
     public void checkVisibleRange(int includeIndex) {
-        int start = Math.min(table.getTopIndex() - 1, includeIndex);
-        int length = Math.max(table.getVisibleItemCount(), includeIndex - start);
+        int start = table.getTopIndex();
+        int length = table.getVisibleItemCount() - 1;
         Range r = lastRange;
 
     	if (start != r.start || length != r.length) {
@@ -311,7 +311,7 @@
 
 	        // Compute the currently visible range
 	        int start = Math.min(table.getTopIndex(), knownObjects.length);
-	        int length = Math.min(table.getVisibleItemCount(), knownObjects.length - start);
+	        int length = Math.min(table.getVisibleItemCount() - 1, knownObjects.length - start);
 	        int itemCount = table.getItemCount();
             
         	int oldStart = lastRange.start;
@@ -328,7 +328,7 @@
 				int row = idx + oldStart;
 				
 				// If this item is no longer visible
-				if (row < itemCount && (row < start || row >= start + length)) {
+				if (row < itemCount && (row < start || row > start + length)) {
 					
 					// Note: if we wanted to be really aggressive about clearing
 					// items that are no longer visible, we could clear here unconditionally.
Index: src/org/eclipse/jface/viewers/deferred/DeferredContentProvider.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jface/src/org/eclipse/jface/viewers/deferred/DeferredContentProvider.java,v
retrieving revision 1.13
diff -u -r1.13 DeferredContentProvider.java
--- src/org/eclipse/jface/viewers/deferred/DeferredContentProvider.java	9 May 2008 14:12:51 -0000	1.13
+++ src/org/eclipse/jface/viewers/deferred/DeferredContentProvider.java	16 Apr 2010 12:12:12 -0000
@@ -101,7 +101,7 @@
 			Rectangle rect = table.getClientArea ();
 			int itemHeight = table.getItemHeight ();
 			int headerHeight = table.getHeaderHeight ();
-			return (rect.height - headerHeight + itemHeight - 1) / (itemHeight + table.getGridLineWidth());
+			return (rect.height - headerHeight + itemHeight - 1) / itemHeight;
 		}
 		
 		/* (non-Javadoc)