Need Help getting my Gen6 w/ marlin to work

[km28104]

I'm new to 3d printing and can't seem to get this Prusa Mendel 3d printer set up correctly.

I'm using a gen6 board from makerfarm.com with the latest version of Marling compiled in Arduino v023.
Firmware compiles and uploads with no errors.

Using opto enstops that came with the board.

Using Pronterface as print control

Each axis will move in the + direction any number of steps I want, but will only move in the - direction the same number of steps and no further.
Homing the y axis seems to work, but neither the X or the Z axis recognize the endstops.

I know I must be doing something wrong, but don't know what it is.

any help would be appreciated.

Ken