The default port doesn't work with solo mining for some reason... I changed mine to 2XXX and it works fine.
FWIW The difficulty is 0.61 not 0.21 as coinchoose says. That means it's barely above LTC for mining profitability at the moment.
You need to add "port=12127" to your emerald.conf to solo mine. It wouldn't work for me with just the rpcport in the conf.