Re: [ANN][SYNC]X11 | POS| 1,000 Coins| Mandatory Update - HARD FORK AT 8210
YOU DONT HAVE TO DELETE THE BLOCKCHAIN - JUST SHUT THE WALLET AND REOPEN IT - thats all and it will smoothly going on 
doesn't change a thing. have done that a few times.In that case, just rename the folder and let it make a new one. If it works, you can copy across the wallet.dat file and delete the renamed folder.