XF 1.1 Invalid model 'XenForo_Model_ForumWatch' specified


Error when trying to post new threads.

Invalid model 'XenForo_Model_ForumWatch' specified
XenForo_Model::create() in XenForo/DataWriter.php at line 1892
XenForo_DataWriter->getModelFromCache() in bdTagMe/XenForo/DataWriter/DiscussionMessage/Post.php at line 21
bdTagMe_XenForo_DataWriter_DiscussionMessage_Post->_postSaveAfterTransaction() in XenForo/DataWriter.php at line 1399
XenForo_DataWriter->save() in XenForo/DataWriter/Discussion.php at line 415
XenForo_DataWriter_Discussion->_saveFirstMessageDw() in XenForo/DataWriter/Discussion.php at line 363
XenForo_DataWriter_Discussion->_postSave() in XenForo/DataWriter.php at line 1385
XenForo_DataWriter->save() in XenForo/ControllerPublic/Forum.php at line 490
XenForo_ControllerPublic_Forum->actionAddThread() in XenForo/FrontController.php at line 310
XenForo_FrontController->dispatch() in XenForo/FrontController.php at line 132
XenForo_FrontController->run() in /home7/rosspres/public_html/index.php at line 13
This originated when I used the Update Checker to try to update Template Modification System add-on. Apparently you first had to update XenForo to version 1.2, which I have not yet gotten round to doing (at the time I was unaware that XenForo was due for an update).

Thanks in advance.