Some bitcoin clients wont accept block 277956 for some reason.

This is some #bitcoin-dev discussion about the issue:
http://bitcoinstats.com/irc/bitcoin-dev/logs/2013/12/29
http://bitcoinstats.com/irc/bitcoin-dev/logs/2013/12/30 <- Ukyo asked for some advice in this one.

Even http://blockexplorer.com/ is stuck on block 277955.