I have a problem in Altium Designer were if I define some net classes in the pcb editor the next time I load the design they have gone. Has anyone else seen this happen.
usually you should place directive net classes in schematics(make sure Net class generation is checked in project options) but if you define net class in PCB then you should go to project options and under ECO generation find Remove Net Classes and in front of it select do not generate changes. then you 'll be ok.
cheers