Hello All,

Josh Rickmar and I discovered a subtle consensus change in Bitcoin Core
which causes forking behavior on regtest.  Luckily it does not affect
mainnet or testnet, however it does mean that regtest difficulty
retargetting is broken.

I've made a post to the bitcointalk forums at
https://bitcointalk.org/index.php?topic=1065504 for the nicer formatting
which explains in detail.

Regards,

Dave Collins