First of all, thank you optiminer for your work with this miner. It is by far the highest performing one. However it behaves a bit erratically. For example, I use a rig with 4x290x cards (actually it's 2x295x2s) and without apparent reason, it stopped mining on two of them at one point. The cards are rock solid stable and they've never skipped a beat with Claymore's miner or previous scrypt miners. Please see the log below in case you have any suggestions   (do note that from 18:39, only 2 GPUs seem to be mining anymore)