Happened a DOS attack and the blockchain broke on February 12, which made mining impossible until 4 days ago that the blockchain was fixed and three days ago the blockexplorer is synchronized can look for yourself. I think the mining is currently in block 71365. I think the code was changed or updated, and I think you should make a clean installation of the wallet again to make it work. Because I had to perform that process because since the blockexplorer was updated the wallet did not work and now with the new installation is ok