B&D cmm1000 blade replacement

[kelbykcotton]

After sharpening my blade on the Black and Decker CMM1000, I find I am unable to stop the shaft from turning so that I can tighten the nut. I've done this countless times with the wood block against the blade, etc., but with the CMM1000 the shaft simply turns with the nut. Spacers and guards are replaced as required according to the manual. There is no missing part. Ideas?