Infinite loop when workflow runs

Hi all,

I created a workflow that updates values in an entity and send mails. It was working until today morning. Now when I try to run, I get this error.

"This workflow job was canceled because the workflow that started it included an infinite loop. Correct the workflow logic and try again. For information about workflow logic, see Help."

I have not used any pluggins. Please suggest what could be the wrong step here.

Regards 

Deepak Kumar