Blame Greece's debt crisis for contributing to the recent drop in your stock portfolio, but give it credit for something that could benefit consumers: lower mortgage rates. Last week, rates on fixed-rate mortgages fell to their lowest level this year, while rates on adjustable-rate loans dipped to a point not seen for years, according to a weekly survey by mortgage giant Freddie Mac. The average 30-year fixed-rate mortgage slipped to 4.93% last week, down from 5% the week before and down to the lowest level since early December.