diff -ruN original/views_nivo_slider.module mod/views_nivo_slider.module
--- original/views_nivo_slider.module	2010-06-18 22:04:17.000000000 +0700
+++ mod/views_nivo_slider.module	2012-01-03 17:11:33.000000000 +0700
@@ -139,7 +139,12 @@
     }
   }
 
-  $img = theme('imagecache' , $presetname , $image_url, $title, $title, $attributes, TRUE);
+  if (!empty($presetname)) {
+    $img = theme('imagecache' , $presetname , $image_url, $title, $title, $attributes, TRUE);
+  }
+  else {
+    $img = theme('image', $image_url, $title, $title, $attributes, TRUE);
+  }
 
   if ($link) {
     $img = '<a href="'.$link.'" class="views-processed">'.$img.'</a>';
diff -ruN original/views_nivo_slider_style_plugin.inc mod/views_nivo_slider_style_plugin.inc
--- original/views_nivo_slider_style_plugin.inc	2010-06-18 22:04:17.000000000 +0700
+++ mod/views_nivo_slider_style_plugin.inc	2012-01-03 17:38:27.000000000 +0700
@@ -41,11 +41,13 @@
     foreach (imagecache_presets() as $p) {
       $presets[$p['presetname']] = $p['presetname'];
     }
+
+    $preset_options = array('' => t('<original>')) + $presets;
     
     $form['imagefield_preset'] = array(
       '#type' => 'select',
       '#title' => t('Image field Preset'),
-      '#options' => $presets,
+      '#options' => $preset_options,
       '#default_value' => $this->options['imagefield_preset'],
       '#description' => t('Select the imagecache preset to apply on image field.'),
     );
@@ -114,11 +116,6 @@
       ),
     );
 
-    $presets = array();
-    foreach (imagecache_presets() as $p) {
-      $presets[$p['presetname']] = $p['presetname'];
-    }
-
     $form['controlNavThumbsIC'] = array(
       '#type' => 'select',
       '#title' => t('ImageCache presets for use in thumbs'),
@@ -192,6 +189,18 @@
     );
 
   }
+  
+  function options_validate(&$form, &$state) {
+    parent::options_validate($form, $state);
+    
+    $values = $state['values']['style_options'];
+    
+    if (empty($values['imagefield_preset']) && $values['controlNav'] == 'thumbsIC') {
+      form_error($form['controlNav'], t("Control Navigator %type can't be used with original image.", array(
+        '%type' => t('Thumbnails with ImageCache presets'),
+      )));
+    }
+  }
 
   function get_style_options() {
     return array(