I have a new 2010 Sears Craftsman YTS3000 42" tractor with mulching blades. It seems like when I make a pass there is a high spot in the middle ( as if in the center of the 2 blades) that does not get cut.

Hi,
This is an occurrence that could be caused by bent blade(s) or deck shell if something has been struck, but is commonly the result of cutting too long grass, moving to fast or very sharp turns in one direction.
Peace,
Clarke

Thanks, I will slow it down next cut and see if that helps for starters...