Android Exception 6 (adapter is not modified from a background thread)

07-23 09:47:34.962: E/AndroidRuntime(7001): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131230794, class com.tongyan.widget.view.PullToRefreshListView) with Adapter(class android.widget.HeaderViewListAdapter)]07-23 09:47:34.962: E/AndroidRuntime(7001): jav