Just now, I was playing magento 126.96.36.199 happily.
However, suddenly, I cannot login in my account at backend.
I tried my second account but it was still failed. I then find that all the login features including frontend member login fail to function.
Account registration was success but it does not direct me to the success registration message.
I hosted magento on fedora with fully qualified domain.
I have no idea why this happened.