diff --git a/h5p-development.class.php b/h5p-development.class.php
index 75e9daf..7f33689 100644
--- a/h5p-development.class.php
+++ b/h5p-development.class.php
@@ -93,6 +93,7 @@ class H5PDevelopment {
     // TODO: Should we remove libraries without files? Not really needed, but must be cleaned up some time, right?
 
     // Go trough libraries and insert dependencies. Missing deps. will just be ignored and not available. (I guess?!)
+    $this->h5pF->lockDependencyStorage();
     foreach ($this->libraries as $library) {
       $this->h5pF->deleteLibraryDependencies($library['libraryId']);
       // This isn't optimal, but without it we would get duplicate warnings.
@@ -104,6 +105,7 @@ class H5PDevelopment {
         }
       }
     }
+    $this->h5pF->unlockDependencyStorage();
     // TODO: Deps must be inserted into h5p_nodes_libraries as well... ? But only if they are used?!
   }
 
diff --git a/h5p.classes.php b/h5p.classes.php
index 7d964ba..5940e06 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -408,6 +408,17 @@ interface H5PFrameworkInterface {
    */
   public function deleteLibraryDependencies($libraryId);
 
+  /**
+   * Start an atomic operation against the dependency storage
+   */
+  public function lockDependencyStorage();
+  
+  /**
+   * Stops an atomic operation against the dependency storage
+   */
+  public function unlockDependencyStorage();
+  
+  
   /**
    * Delete a library from database and file system
    *
@@ -1433,7 +1444,7 @@ Class H5PExport {
       'title' => $content['title'],
       // TODO - stop using 'und', this is not the preferred way.
       // Either remove language from the json if not existing, or use "language": null
-      'language' => isset($content['language']) ? $content['language'] : 'und',
+      'language' => (isset($content['language']) && strlen(trim($content['language'])) !== 0) ? $content['language'] : 'und',
       'mainLibrary' => $content['library']['name'],
       'embedTypes' => $embedTypes,
     );
@@ -1465,7 +1476,7 @@ Class H5PExport {
 
     // Create new zip instance.
     $zip = new ZipArchive();
-    $zip->open($zipPath, ZIPARCHIVE::CREATE);
+    $zip->open($zipPath, ZIPARCHIVE::CREATE | ZIPARCHIVE::OVERWRITE);
 
     // Get all files and folders in $tempPath
     $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($tempPath . DIRECTORY_SEPARATOR));
@@ -1648,19 +1659,23 @@ class H5PCore {
 
     // Update content dependencies.
     $content['dependencies'] = $validator->getDependencies();
-    $this->h5pF->deleteLibraryUsage($content['id']);
-    $this->h5pF->saveLibraryUsage($content['id'], $content['dependencies']);
 
-    if ($this->exportEnabled) {
-      // Recreate export file
-      $exporter = new H5PExport($this->h5pF, $this);
-      $exporter->createExportFile($content);
+    // Sometimes the parameters are filtered before content has been created
+    if ($content['id']) {
+      $this->h5pF->deleteLibraryUsage($content['id']);
+      $this->h5pF->saveLibraryUsage($content['id'], $content['dependencies']);
 
-      // TODO: Should we rather create the file once first accessed, like imagecache?
+      if ($this->exportEnabled) {
+        // Recreate export file
+        $exporter = new H5PExport($this->h5pF, $this);
+        $exporter->createExportFile($content);
+
+        // TODO: Should we rather create the file once first accessed, like imagecache?
+      }
+
+      // Cache.
+      $this->h5pF->setFilteredParameters($content['id'], $params);
     }
-
-    // Cache.
-    $this->h5pF->setFilteredParameters($content['id'], $params);
     return $params;
   }
 
@@ -2184,7 +2199,7 @@ class H5PCore {
     $platformInfo['uuid'] = $this->h5pF->getOption('h5p_site_uuid', '');
     // Adding random string to GET to be sure nothing is cached
     $random = substr(str_shuffle("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"), 0, 5);
-    $json = $this->h5pF->fetchExternalData('http://h5p.lvh.me/h5p.org/libraries-metadata.json?api=1&platform=' . urlencode(json_encode($platformInfo)) . '&x=' . urlencode($random));
+    $json = $this->h5pF->fetchExternalData('http://h5p.org/libraries-metadata.json?api=1&platform=' . urlencode(json_encode($platformInfo)) . '&x=' . urlencode($random));
     if ($json !== NULL) {
       $json = json_decode($json);
       if (isset($json->libraries)) {
@@ -2316,7 +2331,7 @@ class H5PContentValidator {
    */
   public function validateContentFiles($contentPath, $isLibrary = FALSE) {
     if ($this->h5pC->disableFileCheck === TRUE) {
-      return TRUE; 
+      return TRUE;
     }
 
     // Scan content directory for files, recurse into sub directories.