HFSS 15 windows 7 error unable to locate or start COM engine

i am designing a microstrip monopole antenna , and after checking ,,, i wasn't able to analyze ,, when i press analyze , i got that error: Unable to locate or start COM engine on 'Local Machine' : no response from COM engine, timed out (10:22:47 PM Jan 24, 2015)
i don't know why ?