Would need to know more about the setup and wiring to really offer any constructive help. Normally the things that destroy drivers are having the steppers disconnected under load. Do you have limits that cut power to part of the rig, that got tripped upon first movement because they were either tripped or had the wrong input value?
The G540's are pretty bulletproof, so unless you changed a switch setting or disconnected a stepper under load, it's very hard to tell what went wrong.
Have you also ruled out any issues with whatever PSU you're using?
cheers, Ian