Not sure but according to other forums that I have read your is a fairly common question, unfortunately, Sears never seems to have an answer (other than doing the things you have already done). Just make sure the blades are on correctly. I have the same mower and have replaced the blades and if memory serves me correctly, there is a 'right' and 'wrong' way to put them on. I'm assuming though that you had this problem first which resulted you in putting on the new blades? Sorry I didn't offer any help but I wanted you to know that apparently its also a problem that plagues others as well.
bmiller, June 2006
