I have been using a Stepcraft 600 for over a year with no problems. I needed to change the PC it was connected to and that's when the problem started. I now have a permanent Reset condition that I cannot override. The limit switches are all physically OFF, as is the ESwitch but the Diagnostic Limit, Home and Estop indications are all Green. Making/Breaking any of the switches does not change the indications.
Reconnecting the original PC made no difference.
The plot thickens!
Turns out the 'solution' was not repeatable and subsequently the UCCNC and Stepcraft programmes kept opening in Demo Mode, meaning the CNC machine was unusable.
Eventually discovered that the UC100 was not appearing in the Device Manager list. After trying numerous things I finally determined that the Stepcraft machine has to be powered off while the PC is booting up. Once the PC has booted, and correctly recognised the UC100 as an active device, the Stepcraft programme can be opened and the machine powered up.
According to Rory (kudos for answering emails on a Sunday!), the Stepcraft must be loading the UC100 to the point it can't synch with the PC and hence is not seen as an active device. The 'loading' must be right on the threshold which is why it occasionally worked.