I've now experienced this twice with my Delta 1010. I'm using the released drivers. For some reason, certain ports just stop sending audio. I'll be using output 7/8 in forge and I'll listen to some audio on the internet and suddenly my port 7/8 stops working. Even after I reboot. I have to switch to another set of ports. I'm down to ports 3/4 now. The only way around it is to uninstall and reinstall the drivers.
Very strange, no? It's like the port gets permanently locked somehow...