...

src/calibre/gui2/dialogs/check_library.py

@@ -74,6 +74,7 @@ class DBCheck(QDialog):
             self.reject()
 
     def start_load(self):
+        try:
             self.conn.close()
             self.pb.setMaximum(self.count)
             self.pb.setValue(0)
@@ -89,6 +90,11 @@ class DBCheck(QDialog):
             self.conn.commit()
 
             QTimer.singleShot(0, self.do_one_load)
+        except Exception, e:
+            import traceback
+            self.error = (as_unicode(e), traceback.format_exc())
+            self.reject()
+
 
     def do_one_load(self):
         if self.rejected: