Odd... was the manure spread evenly or could it be in clumps here and there and not in other places? Have you tested your soil pH? If soils are either strongly acid or strongly alkaline, that can lock up the nitrogen in the soil so that it is not available any more. ( http://www.avocadosource.com/tools/Fert ... les/pH.htm
Anything else you can tell us? Did you mulch it? Sometimes if you put down wood chip mulch, trying to break down the carbon can suck nitrogen back out of the soil.
Just trying to think of things that could account for what you are seeing... maybe others will have more ideas...