This may be a corrupt blockchain ...

Now this will not be a positive thing to hear, but a full resync is probably what you will need. In order to do that, you will need to delete the BlockChain component from your SWEEP folder (which is pretty much everything EXCEPT the wallet.dat and SweepstakeCoin.conf file if you have one), and then ropen/restart the wallet. ALWAYS backup your wallet by making a copy of your wallet.dat file or keep your private keys somewhere safe, or both.

The issue with this is that the BlockChain takes a huge amount of time of late to sync, which is something that really can't be pushed in anyway, even by a bootstrap.

Current working nodes are all listed here - https://chainz.cryptoid.info/sweep/#!network - which you can add to the .conf file, but it will still take some time before you download the entire BlockChain.

Let us know how you fare with it all.

#crysx