Index: t3lib/extjs/class.t3lib_extjs_extdirectapi.php
===================================================================
--- t3lib/extjs/class.t3lib_extjs_extdirectapi.php	(revision 7796)
+++ t3lib/extjs/class.t3lib_extjs_extdirectapi.php	(working copy)
@@ -64,19 +64,25 @@
 	public function getAPI($ajaxParams, TYPO3AJAX $ajaxObj) {
 		$filterNamespace = t3lib_div::_GET('namespace');
 
+		// Check parameter clear_cache
+		$clearCache = t3lib_div::_GET('clear_cache') ? TRUE : FALSE;
+		
 		// look up into the cache
 		$cacheIdentifier = 'ExtDirectApi';
 		$cacheHash = md5($cacheIdentifier . $filterNamespace . serialize($this->settings));
 		$cacheContent = t3lib_pageSelect::getHash($cacheHash);
 
 		// generate the javascript content if it wasn't found inside the cache and cache it!
-		if (!$cacheContent) {
+		// if $clearCache is detected, replace the old cache by the new one
+		if (!$cacheContent || $clearCache) {
 			$javascriptNamespaces = $this->generateAPI($filterNamespace);
-			t3lib_pageSelect::storeHash(
-				$cacheHash,
-				serialize($javascriptNamespaces),
-				$cacheIdentifier
-			);
+			if (!empty($javascriptNamespaces)) {
+				t3lib_pageSelect::storeHash(
+					$cacheHash,
+					serialize($javascriptNamespaces),
+					$cacheIdentifier
+				);
+			}
 		} else {
 			$javascriptNamespaces = unserialize($cacheContent);
 		}
@@ -104,6 +110,23 @@
 				$setup . 'Ext.app.ExtDirectAPI = Object.extend(Ext.app.ExtDirectAPI, |);'
 			);
 		}
+		else {
+			$errorMessage[] = 'Ext Direct error in \"' . __CLASS__ . '\" with namespace: \"' . $filterNamespace .'\"';
+			$errorMessage[] = 'Try to clear the TYPO3 cache and / or use paramater clear_cache=1 as parameter in URL typo3/ajax.php';
+			$errorMessage[] = '\nCheck also the following points:';
+			$errorMessage[] = '- configuration in ext_localconf.php: registration key should be like \"TYPO3.MyExtension.Sample\"';
+			$errorMessage[] = '- URL typo3/ajax.php: namespace parameter should be like: \"TYPO3.MyExtension\"';
+			$errorMessage[] = '- javascript: method\'s name should be like: \"TYPO3.MyExtension.Sample.myMethod\"';
+			$ajaxObj->setContentFormat('javascript');
+			$ajaxObj->setJavascriptCallbackWrap('
+				errorMessage = "' . implode('\n', $errorMessage) . '";
+				if (typeof console == "object") {
+					console.log(errorMessage);
+				} else {
+					alert(errorMessage);
+				}	
+			');
+		}
 	}
 
 	/**