XF 1.2 Error when trying to register -- registration not working

I'm having a problem with my XenForo forum. When you attempt to register, you get an error (it varies based upon browser, but it shows "no data received" for me in Chrome). I have the same issue in Firefox.

I'm not sure where to start with this, but here's my forum if you want to try for yourself: http://emeraldsmc.com/login/

I've found that the error occurs if something is entered in the dropdown username box before pressing "sign up", and clearing that box takes you to the registration page successfully, but once you fill out the information on that page you'll get the same error.

Any help?
I have a new issue, I attempted uninstalling an add-on and now get this error when visiting my forums:
An exception occurred: Mysqli prepare error: Table 'emeraldsmc_forum.hd_serverstatus_servers' doesn't exist in /usr/www/emeraldsmc/public/library/Zend/Db/Statement/Mysqli.php on line 77

[*]Zend_Db_Statement_Mysqli->_prepare() in Zend/Db/Statement.php at line 115
[*]Zend_Db_Statement->__construct() in Zend/Db/Adapter/Mysqli.php at line 381
[*]Zend_Db_Adapter_Mysqli->prepare() in Zend/Db/Adapter/Abstract.php at line 478
[*]Zend_Db_Adapter_Abstract->query() in XenForo/Model.php at line 219
[*]XenForo_Model->fetchAllKeyed() in HeroDev/ServerStatus/Model/Server.php at line 63
[*]HeroDev_ServerStatus_Model_Server->getAllServers() in EWRporta/Block/ServerStatus.php at line 8
[*]EWRporta_Block_ServerStatus->getBypass() in EWRporta/Model/Blocks.php at line 135
[*]EWRporta_Model_Blocks->getBlockParams() in EWRporta/ViewPublic/Custom.php at line 71
[*]EWRporta_ViewPublic_Custom->renderHtml() in XenForo/ViewRenderer/Abstract.php at line 227
[*]XenForo_ViewRenderer_Abstract->renderViewObject() in XenForo/ViewRenderer/HtmlPublic.php at line 67
[*]XenForo_ViewRenderer_HtmlPublic->renderView() in XenForo/FrontController.php at line 572
[*]XenForo_FrontController->renderView() in XenForo/FrontController.php at line 158
[*]XenForo_FrontController->run() in /usr/www/emeraldsmc/public/index.php at line 13
Clearly it's an issue with the add-on but it's something that was badly coded and the author has disappeared. Any ideas on how to fix it?