boolean not working (did remove doubles and flipped normals...) I've ran into an boolean problem, and even after trying several solution found online, I cant get it to work.

I've made some letters converted them to mesh, duplicated them, made those duplicates thinner and now want to cut  these from the thicker ones.

On two letters (S,E) it works. But the "T" doesn't.
I transformed both T-meshes to quads, removed doubles and flipped normals, but still its not working.

I've uploaded the file, and would be glad if someone could explain to me, how to fix that.:
http://www.lyzarr.com/stuff/help.blend

thanks
your "carving" T shape has some mesh issue: here in face select mode I circled something surely wrong...  (front and back of the shape)



it should be just that. no, wait also the base mesh has similar issues in the "T" mesh island... (front and back of the shape)