The "FeralHeart.exe has stopped working" can be solved by simply removing, then re-downloading FeralHeart again. To also help that issue, turn off the water reflection, and turn down the viewing distance.
As for the account problem, if that account is old or unused, sometimes they do get missplaced or deleted, but if that is not the case, make sure your names are PERFECT AND RIGHT. If that is not the case, I would say to PM an admin or mod about this issue.