diff --git a/src/calibre/ebooks/__init__.py b/src/calibre/ebooks/__init__.py
index a084cdd0f8..dcd5604aa8 100644
--- a/src/calibre/ebooks/__init__.py
+++ b/src/calibre/ebooks/__init__.py
@@ -25,7 +25,7 @@ class DRMError(ValueError):
 BOOK_EXTENSIONS = ['lrf', 'rar', 'zip', 'rtf', 'lit', 'txt', 'htm', 'xhtm',
                    'html', 'xhtml', 'pdf', 'pdb', 'prc', 'mobi', 'azw', 'doc',
                    'epub', 'fb2', 'djvu', 'lrx', 'cbr', 'cbz', 'oebzip',
-                   'rb', 'imp', 'odt', 'chm']
+                   'rb', 'imp', 'odt', 'chm', 'tpz', 'azw1']
 
 class HTMLRenderer(object):
 
diff --git a/src/calibre/gui2/main.py b/src/calibre/gui2/main.py
index b57387033d..37d40f25fb 100644
--- a/src/calibre/gui2/main.py
+++ b/src/calibre/gui2/main.py
@@ -385,7 +385,7 @@ class Main(MainWindow, Ui_MainWindow, DeviceGUI):
                 self.action_view, self.action_save, None, None)
         QObject.connect(self.library_view,
                 SIGNAL('files_dropped(PyQt_PyObject)'),
-                        self.files_dropped)
+                        self.files_dropped, Qt.QueuedConnection)
         for func, target in [
                              ('connect_to_search_box', self.search),
                              ('connect_to_book_display',