I got this working on Ubuntu under a virtual machine in the end, but I had to hash out the last seed-note as show below in order get passed similar errors:
seed-node = 212.47.249.84:40696
seed-node = 52.4.250.181:39705
seed-node = 81.89.101.133:2001
seed-node = 192.99.4.226:2001
seed-node = 46.252.27.1:1337
#seed-node = seed.steemd.com:34191
So tried this on OS X, and managed to get it to mine, but it has since started acting up again and started chucking out error messages and terminating. The Virtual Machine running Ubuntu is almost good enough, but it is limited to 16 cores/threads for some reason, when I have 24 available on my machine.