Greetings!
We are sorry for the delay in getting back to you! Thank you very much for your patience and understanding while we found a resolution for this issue. We have a workaround for the problem where you can't log in after joining a specific guild! Please change the language of your game to German or French, which will allow you to login and leave the guild. To do this, click on the golden cog in the upper-right in the launcher. Keep your megaserver the same, but do select another language, and hit "apply." A short patch will occur, which will update the language. Once that has complete, login and leave the guild. After leaving the guild, you may change your language back to English. We do not advise re-joining the guild that caused this issue once you are able to login again until a solution is found.
Again, thank you so much for waiting while we figured out a fix for this issue! It is much appreciated. Please let me know if you have any other questions or concerns, I would be happy to assist you however I can. If you have already resolved this issue yourself or with the help of another agent, I apologize for the extra email. Have a great day!
Thank you for your continued interest and support!
Warm Regards,
The Elder Scrolls Online Team