Index: /branches/release-36/lib/MT/Entry.pm
===================================================================
--- /branches/release-36/lib/MT/Entry.pm (revision 1920)
+++ /branches/release-36/lib/MT/Entry.pm (revision 2043)
@@ -364,6 +364,7 @@
         my $entry   = MT::Entry->load( $comment->entry_id )
             or return;
-        if ($comment->visible) {
-            $entry->comment_count( $entry->comment_count - 1 );
+        if ( $comment->visible ) {
+            my $count = $entry->comment_count > 0 ? $entry->comment_count - 1 : 0;
+            $entry->comment_count($count);
             $entry->save;
         }
@@ -414,5 +415,6 @@
                 my $entry = MT::Entry->load( $tb->entry_id )
                     or return;
-                $entry->ping_count( $entry->ping_count - 1 );
+                my $count = $entry->ping_count > 0 ? $entry->ping_count - 1 : 0;
+                $entry->ping_count($count);
                 $entry->save;
             }