I have the EXACT problem with mine. I have also lost the rubber guard around the bottom. Did you ever figure out what the problem was? I too had new blades put on (not sure what kind) and when I told the tech what it was doing he took those off and put my old ones back on and it STILL does it. I am completely covered in dirt when I get off the mower. I also got the answer that "maybe it's just dead dry grass" WRONG! I have had mine for over 7 years and have NEVER had this problem. Any help would be appreciated.