Index: multiblock.module
===================================================================
--- multiblock.module	(revision 397)
+++ multiblock.module	(working copy)
@@ -90,7 +90,15 @@
           '#value' => $block_info->delta,
       );
     }
-    return module_invoke($block_info->module, 'block', $op, $block_info->orig_delta, $edit);
+    if ($op == 'view') {
+      $block = module_invoke($block_info->module, 'block', $op, $block_info->orig_delta, $edit);
+      $block['orig_module'] = $block_info->module;
+      $block['orig_delta'] = $block_info->orig_delta;
+      return $block;
+    }
+    else {
+      return module_invoke($block_info->module, 'block', $op, $block_info->orig_delta, $edit);
+    }
   }
   // No such multiblock, shouldn't ever happen.
   return;
@@ -274,6 +282,17 @@
 }
 
 /**
+ * Implementation of hook_preprocess_block()
+ *   Add "{orig_module}-{orig_delta}-instance" class to multiblock blocks
+ *   Requires a block_classes-aware theme like Zen...
+ */
+function multiblock_preprocess_block(&$vars) {
+  if ($vars['block']->module == 'multiblock') {
+    $vars['block_classes'][] = $vars['block']->orig_module . '-' . $vars['block']->orig_delta . '-instance';
+  }
+}
+
+/**
  * Theme function for the "Manage Block Instances" page.
  */
 function theme_multiblock_general($add_block_form, $multiblocks) {