Mandatory wallet update v4. 5 chain rollback (April 1, 2018). This update will roll back the chain to block 263536.

01 Apr 2018, 19:16
Mandatory wallet update v4.5 chain rollback (April 1, 2018) This update will roll back the chain to block 263536. All fraudulent transactions that were made after this block are invalid on the new blockchain.