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.
i am nearly 60. Pls explain what you mean by that.
No worries, you are still not old enough to be my father..

The folder where you have the Sync.conf and wallet.dat, usually in C:\Users\yourname\AppData\Roaming\Sync
If you close the program, rename "Sync" to "SyncBak", then start the program again to see if it will download the full blockchain.
If it does, just close down the program again, copy the Sync.conf and wallet.dat from "SyncBak" to "Sync" and you're all good