I have this error if i try to generate the command : Sorry, an unexpected error occurred
this means pool is offline, because probably background pool dev doing some job at that moment so try again later please.
you will see when command builder become online & used; it returns "command to use" and you can use it as a first pool in pools at cgminer so when pool gets back online cgminer or miner software detects its online and pool666 can then start accepting shares from you.
i'll let you know when pool is back online but its better you use the above tactics.
You are a kind person. Thank you for this detail explanation. I also encountered this error before.