A small fork has been detected on the network. It is actively being corrected. Please check your Sterlingcoin wallet's block height against that of either explorer:
https://chainz.cryptoid.info/slg/ or
http://transactions.sterlingcoin.org , they are both correct.
If you find your block height does not match that of the explorers, recent snapshots are available on the website and under the 'Download' navigation.
Sorry for any inconvience.