Thank you so much for the quick respond. I'm getting GPU 0, GpuMiner cu_k1 failed 77, an illegal memory access was encountered in claymore and CUDA failure 77: an illegal memory access was encountered ; in Genoil, after a few seconds of mining.
Also in ZEC it says CUDA: Device: 3 Thread exited with code: 77
or CUDA: Device: 3 Thread exited with code: 64
Try a lower memory overclock offset: I get these errors when I overclock too much. To confirm, check the output of "dmesg" in the terminal; if you get messages like these:
[139035.343237] NVRM: Xid (PCI:0000:02:00): 31, Ch 0000001b, engmask 00000101, intr 10000000
Most probably that's the issue. If you get these messages but with a different Xid (in this example it's 31), report here, as each code has a different meaning.