i had the same problem after upgrading.
it's because you are on the wrong (old) chain.
this probably happens if you upgraded a little too late.

you need to backup your wallet (save the wallet.dat somewhere safe), close it, and then deinstall the wallet or delete the wallet files in the roaming folder.
then you start the exe file again to start a fresh install.
then you sync it again (use bootstrap to sync faster).
when you have syncronized totally you close the wallet and copy your saved wallet.dat into the new roaming folder and start wallet again and you should be fine.