So having got the thing sort of working I set about checking out the axes and sorting a few problems with the stepper drivers (enable iffy). This involved turning the PC on and off a few times and changing/saving the configuration in UCCNC once or twice, but no messing with owt else on the PC. Just thought I'd cracked the last issue, turned the PC back on and UCCNC won't start, gives the error "screen file not found". Anyone got any ideas on this please?