I get invalid nonce count -HW errors sometimes. Usually when i first start sgminer. Sometimes I'll have to just restart it, sometimes I'll have to reboot. Once it starts mining though, its usually stable. I might have to restart once a week. But sometimes it does take several crash and restarts before it goes. I have no idea what causes that.
You can try my sgminer.conf. I use it for a 7950, but I edited the gpu engine and memclock to defaults and lowered intensity to 15 (from 17). I use this conf on my 7950 and my 280x. Be sure to edit your pool info. And you should add some backup pools as well one you get things working.
{
"pools" : [
{
"url" : "stratum+tcp://mining.darkcointalk.org:3333",
"user" : "marduk.7950",
"pass" : "x"
}
],
"auto-fan" : true,
"intensity" : "15",
"worksize" : "64",
"kernel" : "darkcoin-mod",
"lookup-gap" : "2",
"gpu-threads" : "2",
"gpu-engine" : "0",
"gpu-fan" : "65-100",
"gpu-memclock" : "0",
"gpu-memdiff" : "0",
"gpu-powertune" : "20",
"gpu-vddc" : "0.000",
"temp-cutoff" : "80",
"temp-overheat" : "70",
"temp-target" : "65",
"api-mcast-port" : "4028",
"api-port" : "4028",
"expiry" : "1",
"scan-time" : "1",
"failover-switch-delay" : "60",
"gpu-dyninterval" : "7",
"gpu-platform" : "0",
"log" : "5",
"no-pool-disable" : true,
"queue" : "0",
"scan-time" : "1",
"tcp-keepalive" : "30",
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin",
"no-submit-stale" : true
}