Not able to login to Dashboard

Hello there,

I am currently trying to install snapshot on a clients site in order to schedule backups of their database.

At the moment when I go to login to the WP Dashboard in order to activate the plugin etc. it automatically logs me out of Wordpress.

Is this something you have come across before, or have any idea what might be happening.

It is on the live site so I can't really turn off all plugins, though i have tried turning off the anti spam plugin in case that was doing it.

Any help appreciated.