Can you please post your settings? and diamond.conf ? obviously omit true passwords..
I posted my settings several times but i'll do it again
For solo mining, i use a HIS Radeon HD 6950 at GPU clock 930 MHz and Memclock 1350 MHz.
.\sgminer\sgminer.exe -k groestlcoin -o 127.0.0.1:17772 -u yourusername -p yourpassword --intensity 20 -g 2 --thread-concurrency 8192 -w 256 --difficulty-multiplier 0.0039062500
Diamond config.
listen=1
daemon=1
server=1
rpcallowip=*
rpcuser=yourusername
rpcpassword=yourpassword
rpcport=17772
addnode=213.229.0.41
addnode=193.77.159.166
addnode=113.168.158.16