i will answere here, because other thread is not the right place i think. i am afraid not to be a great help, because i have no experince in Mach4. have you worked through all step's of the Manual witch start on page 30?
why should it be something with the ACOI Drivers, when your y-axis Controller is running on the x-axis Outputs of the BOB, and only the new x-axis Driver is not working ?