I've got this error in the forum when I click to a post :

OW Debug - Exception

Message: Invalid error message! File: /homez.541/camikas/www/ow_core/validator.php Line: 70 Trace: #0 /homez.541/camikas/www/ow_plugins/forum/controllers/topic.php(886): OW_Validator->setErrorMessage('') #1 /homez.541/camikas/www/ow_plugins/forum/controllers/topic.php(143): FORUM_CTRL_Topic->generateAddPostForm(1) #2 [internal function]: FORUM_CTRL_Topic->index(Array) #3 /homez.541/camikas/www/ow_core/request_handler.php(266): ReflectionMethod->invokeArgs(Object(FORUM_CTRL_Topic), Array) #4 /homez.541/camikas/www/ow_core/application.php(300): OW_RequestHandler->dispatch() #5 /homez.541/camikas/www/index.php(65): OW_Application->handleRequest() #6 {main} Type: InvalidArgumentException

Any idea?
Thanks.