Your block index file is corrupted.

Close the client, go to C:\Users\(Your Username)\AppData\Roaming\curecoin and delete everything in the folder except for wallet.dat - do not delete wallet.dat or any other wallet file ever under any circumstances Make a backup of the wallet.dat file too.

Then re-open the client. It will have to re-download the entire blockchain.

There are ways to try to repair it, but it's probably not worth the time. It's not a large blockchain to download again.

-Dave