Texturing v. 2.67b problem

hello (i’m new here and already searching for help…sob)
I needed to make a 3d model of a road (nothing more simple!) so i modified the base cube and made it very flat and large. i followed this tutorial for texturing: http://www.youtube.com/watch?v=CzjVDGK8r2I but something went wrong and my superHD asphalt texture became all pixeled and detail-less (and it happened not only with stencil texturing but with every texturing mode and every brush). anybody could provide help? or maybe a better method for texturing?
i so want to get my road done. :c