Can you post your configuration and type of card?
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
sgminer.exe --kernel darkcoin -o stratum+tcp://hiro.suprnova.cc:3313 -u jdebunt.1 -p x --thread-concurrency 8192 -I 13 -g 2 -w 256 --lookup-gap 2 --no-submit-stale --auto-fan --temp-target 74,72
Card 1 : Asus Radeon 280x
Card 2 : Sapphire Radeon 7970