I fixed it! at least it works for me.
I was having the same problem with a couple R9 270s and even (sometimes) a 7970 3Gb card.
I created
ethminer-genoil-chunked: a fork of genoil's miner (from March) that includes a patch from equinox for chunked mining. (The patch was for official ethminer but was never accepted.) All my GPUs are busily mining eth again.
Sorry, no binaries. You will need to compile it yourself. Instructions are in the README.
happy mining.
anybody cured this problem yet, running r9 270 2gb, around 3am this morn it refused to mine ETH, miner clCreateBuffer(-61) GPU can't allocate the DAG in a single chunk, tried all the setx options but still no joy.....
any info gratefully appreciated