After I get to the Zenworks Preboot Menu, I choose what I want to do (in this case, Start Zenworks Imaging Maintenance to pull an image from my server) and the next screen is a black screen with a blinking cursor in the upper left hand portion of the menu. I have no idea why these machines (which are all older, in house built Windows XP machines but still work great) are not getting through to the next step.

Any thoughts?