Weaston,
Did you use the 5UA1200? Below is a link to that page. Are you using a soluble oil at 10% or stronger or is it synthetic? Either way, I would use a heavy duty tapping fluid and turn the coolant off. Solving these problems can be difficult, but satisfying when you get it fixed. You may want to check the Z backlash on your machine using an indicator with the Manual Pulse wheel. If it is within .001", you should be fine.
Dave
http://www.somta.co.za/thr/5ua.htm