could you please post your command line for sgminer ?
ofc.
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 0
start /high sgminer.exe -k darkcoin -o 127.0.0.1:3334 -u x -p x -d 0 -d 1 -w 128 -g 4 --intensity 16,16 --gpu-engine 970,970 --gpu-fan 41,43
had all the same except start /high which shouldn't mean much in cause of my mining system. But I agree, it depends much on distance between me and supernode