A small number of users have reported not being able to login to the front end in Joomla 2.5.13.
This seems to only occur when the users have a corrupt asset table.
This is usually due to a faulty migration from Joomla 1.5, but is not limited to that situation.To check this, look at your asset table in your database. If there is more than one parent_id with a value of 0 this indicates a corrupt table. Run the statement below in the SQL tab of phpMyAdmin when using MySQL.
SELECT count(*) FROM `#__assets` WHERE parent_id = 0
There should only be 1, only the root asset is allowed to have parent_id=0. Find out about the others:
SELECT id, name, title FROM `#__assets` WHERE parent_id = 0 AND id>1
Apply your own prefix instead of #_.
When the name and title are the same you can continue with the fix below. When you have rows with name and title not the same you can't use the statement below jet. You need to fix those first.
To fix you can manually or with an sql query change the parent ids. If the broken assets are categories the parent should be set to the id number for that component (for example usually the id for com_content is 8). (They can also be set to have a parent of another category in the same component.)
UPDATE `prefix_assets` SET `parent_id`=1 WHERE `parent_id`=0 AND id>1
Note: change prefix to your database extension (Global configuration > Server > Database Settings > Database Tables Prefix)
For something besides a category, set the parent_id either to a category asset_id or to the asset_id for the extension if the extension does not use categories.