it also happens to me 2 weeks ago.
I changed to genoil and it continue to work , but today again stop work. Same error claymore ( CUDA error 11 cannot allocate DAG) and genoil (lack of memory).
But I have other miner with NVOC and genoil and it is working correctly.
So I imagined it is a problem of my windows 64bit anniversary. I updated nvidia driver to the last version, but still not working.
ok guys it seems 3gb cards have officially stopped working on eth network. Dag erro etc etc, the 6gb cards in the same rigs are doing fine. surprising though is that under stats its says 2.4gb used for dag.
one by one all the 3gb rigs gave up.
or am i missing something?