What machine are you using?
Parallel port or external motion controller (USB or Ethernet)? Please name model.
Anyway,
Turn off your machine power OFF (NOT the computer - just the router).
Now if you are using stepper motors, Manually turn or crank each motor so that no axis X , Y, Z etc have the limit switch triggered. Just move a little distance.
Now power router on
In MACH3
Click [reset] button
Click [ref. all] button
Let us know how it goes.