displacement woes

I am having a really hard time with displacement.

I got it perfect for my grass, but when I try and do a brick wall…I get weird results…I am taking an acme brick map and applying it to my wall and then a uvw map to scale. Then I am taking the alpha channel of the brick map, which I made…standard blac kand white and using it for my displacement…Either I can not get it lined up right, or I am missing something in the setup…anyone have any suggestions, would be great…

Thanx

Eric

perhaps showing an image and also what kind of displacement type you are using can help to solve this.