please join offical diamond forum http://dmdcoin.net/forum/
there u get infos first and directly from devs

regarding:
WARNING: Checkpoint is too old. Wait for block chain to download, or notify developers.
this will be solved at next wallet version release should be next week

this warning is only visible if u have coins with age above 30 days
coinage is not lost so ur POS minting will kick in again once new wallet is installed