If you guys are having stability issues try adding more RAM. By ram I mean he system memory not video memory.
If you got 4 GPUs you should have at least 8gb.
I think most of the issues are the system ram running out of memory and causing crashes.
Can confirm, low RAM rigs seem to have issues unless given TONS of virtual memory.
I had issues with some 5 GPU rigs with 4GB RAM and 16GB virtual memory, bumped the virtual memory up to 24GB and everything's fine.