locate your nvidia config file inside you XMR STACK folder and open it . You'll see something like this
"gpu_threads_conf" :
[
// gpu: GeForce GT 750M architecture: 30
// memory: 1694/2048 MiB
// smx: 2
{ "index" : 0,
"threads" : 64, "blocks" : 6,
"bfactor" : 6, "bsleep" : 25,
"affine_to_cpu" : false, "sync_mode" : 3,
},

],

Reduce the # of threads by 50% for example 128 = 64, increase your bfactor to 8 if it isn't already. Save and restart the miner, let me know if you still have issues.