Try opening up the whitecoin wallet (basically a mintcoin clone). Then go back and try the mintcoin wallet. If that doesn't work, backup your wallet.dat file and then delete everything and do a fresh install from scratch. Once the wallet is fully synced, replace the wallet.dat file with your backup.

Another option is the to try the salvagewallet command.

From Reddit:
http://www.reddit.com/r/MintCoin/comments/2r0jcn/mintcoin_114_wallet_not_responding/cnjwsgw