ive tried this with cimay several times and got nothing...the only difference is i used 2 tsp. d..m.e. with 1/2 c. of h20, your 1/2c. d.m.e to 1 c. h20 seems a little high gravity. off the top of my head i think `1 c. d.m.e. + 3 qt. h2o is my normal starter rate, so divide that by half you get 1/2c. d.m.e.+1.5 qt h20
im going by Dr. White from whites labs yeast and his recommended 1.040 starting gravity for strarters. he doesnt say you have to use hops either, but i know some people do. i dont, and the advatage is that when you drink the fermented mini-beer you can really taste what the yeast will taste like.
my control for the chimay duds was that after a few days of no signs of fermentation, i put some yeast in from my recent homebrew bottles, and sure enough they fermented out.
i think its the way they store the beer, which is warm. either that or they flash-pasteurize the boyttles before shipping out, killing the yeast.