Hello Addenster,
I also I have the same problem, even tried it right here in oxwall, if access using my facebook account I have no problem, but if I go out and try to enter with a different account I get the following error:
OW Debug - Exception
Message: Invalid email!
File: /home/oxwallo/public_html/ow_system_plugins/base/bol/user_service.php
Line: 721
Trace:
#0 /home/oxwallo/public_html/ow_plugins/fbconnect/controllers/connect.php(102): BOL_UserService->createUser('saraim', '4ceafcf2c6b65', '', NULL, true)
#1 [internal function]: FBCONNECT_CTRL_Connect->login(Array)
#2 /home/oxwallo/public_html/ow_core/dispatcher.php(239): ReflectionMethod->invokeArgs(Object(FBCONNECT_CTRL_Connect), Array)
#3 /home/oxwallo/public_html/ow_core/application.php(290): OW_Dispatcher->dispatch()
#4 /home/oxwallo/public_html/index.php(65): OW_Application->dispatch()
#5 {main}
Type: InvalidArgumentException
Martin