This may happen as not 100% nodes were updated before hard fork.
So you unluckily stuck into abandoned chain looks like.
Simplest and quick way:

1. stop qt wallet
2. backup wallet.dat somewere
3. remove all files in datafolder except wallet.dat
4. place bootstrap.dat in datafolder
5. start qt wallet

bootstrap file is updated up to Jan 23 - bypassing fork point, so you should be safe after resync.
it may take 2-3 hours to load from bootstrap which is much faster then ordinary resync.