'Unspecified error occurred'

I was in a game, the client froze entirely and I tried to restart but now I cannot log in. Upon launch I get an error popup: "Update failed Unspecified error occurred. Please check the logs for more information." When I close the popup and click the Launch button, it makes the new sound but nothing happens for a few seconds, then Launch is greyed out and unclickable.

Please help, I have timed XP boosters on this account because I want to hit 30 :/