It's been my experience with this economy--especially recently--that many landlords are looking more at why the credit history is poor rather than at the actual scores themselves. They seem to be more foregiving of foreclosures than they use to be, as well as debt due to medical, college tuition, divorce, and lost of job (just so long as you have a job or the financial means now to afford the rent--debt to income ratio is very important to landlords.).
Granted, there are still those landlords that require credit scores at or above 640. The very unrealistic ones are those requiring these scores in areas that are economically hit hard.
I would recommend that you have a Realtor represent you. He/She has the expertise to not only find many suitable properties but also to know what questions to ask and information to give to the Landlord or his/her Realtor.