I have about 90% of my mining power pointed at mmpool, that like 0,5 th only. I used to have 1 th but one antminer melted its power connector due to overclocking/bad cables, and other just went berzerk. 1 still working.
Where to buy cheap hashes? mmpool organize get together with paid airplane tickets etc. from mmpool?

*wink wink*
So, it isn't safe to overclock your S3s? (I'm assuming all your antminers are S3s?) Did you use a cheap PSU, were 2 or 4 cables connected when it happened? Sorry to be a bit offtopic, but this is quite interesting information for other S3 users.
I read over on Slush's pool there are specific setting S3 miners should use or else they would have issues on the pool. So, perhaps MMpool has a similiar problem with S3's difficulty or so.