I've got an MC-20 with a Centurion 6 control built in '96; the mill has been working properly until now- it will not boot past the "Initializing Acro-loops" message on the display. At the last shut-down, I had been adjusting the PPU setting for the X-axis in an attempt to decrease the error that I had on that axis (a previous owner had replaced the original ball screw with a metric ball screw, so the PPU had also been changed to match the new screw). I have adjusted this number before with no problems, and do not think I dumb-thumbed it this time, but just want to make sure I note this in case its relevant. After adjusting the PPU, I exited the Parms and entered HDW. As soon as I hit "HDW" the Z axis dove for the table at full rapid; I just barely hit the E-Stop before my Haimer hit the table! I could not remove the Haimer unless I raised the Z-axis a little bit, so I turned the rapids down to zero, crossed my fingers, and hit Reset. Everything worked normally this time, I was able to raise the Z-axis, and jog the X and Y axis' normally. I removed my indicator, and shut the machine down normally. The next boot attempt hung at "Initializing Acro loops", and has been stuck there ever since. I found a cheap used Acro Loop card on eBay from a supposedly working machine, and tried swapping cards (this is a single Acro loop card machine), but this made no difference, still hangs. I'm reading +5.08v, +12.47v, -11.88v on the power supply plug to the AcroLoop card. Any ideas?