ACN5073E None of components entered are in a state to be backed up

My backup for Exchange 2010 started not to work and display the error message below. Could help me.

06/21/2013 18:50:09 ============== Log file pruned using log retention period of 60 day(s)
06/21/2013 18:50:09 ============== No log entries pruned
06/21/2013 18:50:25 ================================================== =======================
06/21/2013 18:50:25 Request : QUERY EXCHANGE
06/21/2013 18:50:25 Exchange Server : (default)
06/21/2013 18:50:25 -------------------------------------------------------------------------
06/21/2013 18:50:32 ACN5073E None of components entered are in a state to be backed up.:confused: