Fixed by erasing all GRC files except gridcoin.conf and wallet.dat then reinstalling wallet from the official site's .msi (v.2.1.0.0 - someone mentionned using 2.1.0.7, but I can't seem to find it). However, the blockchain download progress has been stuck at 0% with message "synchronizing with network" for about 6 hours now, even though I added all nodes and I have 74 active connections. Anyone else has had and fixed this problem?