[Marco van Herwaarden]

If you are using 3.6.8, how come you ignored the warning given when changing the setting? If you set a value less then 60 seconds you will get the following message:

Error: Setting a cookie timeout shorter than 60 seconds could render your board unusable, as you may not have time to enter the control panel to change the cookie timeout value to something longer before you are logged out.

Try running the following queries (after creating a backup!!):

[sql]UPDATE setting set value = 900 WHERE varname = 'cookietimeout';[/sql]
[sql]UPDATE datastore SET data = REPLACE(data, 's:13:"cookietimeout";i:0;', 's:13:"cookietimeout";i:900;') WHERE title = 'options';[/sql]