Steps to reproduce the issue

Unfortunately I don't know what went wrong. I was working on LDAP authentication, and then after logout I couldn't ever again log in.

I tried all the tricks, but Joomla is not moving an inch. It loops quietly to the login form no matter what I do.
I checked the database as well, joomla user is enabled, as is joomla auth :

+--------------+---------------------------+--------+---------+----------+
| extension_id | name | type | enabled | ordering |
+--------------+---------------------------+--------+---------+----------+
| 400 | plg_authentication_gmail | plugin | 0 | 0 |
| 401 | plg_authentication_joomla | plugin | 1 | 1 |

+--------------+-------------------------+-----------+---------+
| extension_id | name | type | enabled |
+--------------+-------------------------+-----------+---------+
| 25 | com_users | component | 1 |
| 216 | mod_users_latest | module | 1 |
| 431 | plg_user_contactcreator | plugin | 0 |
| 432 | plg_user_joomla | plugin | 1 |

I tried to update to 3.5.1, still no change at all. Debug mode not changing anything. Nothing in /logs but an index.html pretty much empty.

I believe the app should tell us something at some point, but it stays mute. Website is working, but backend is completely out of reach...

Expected result

At least an error message!

Actual result

loops back to login

System information (as much as possible)

Debian Wheezy

Additional comments