I had the  same issue with Phoenix miner if I start it with the overclock going on in my Nvidia cards,I start the miner with default settings for the Nvidia cards and then I put in place the overclock,most likely this is a memory issue as I see this when my memory clocks are high enough usually over 1000 for my 3000 series but for the 10 series should start seeing this once you pass the 750 mark.