Locked out of admin

I am running 6.1 iI is still giving me data via the desktop analytics. However I am suddenly locked out of the administration. The reset password works and I have reset the password but it still comes back and says. “Error: Form security key is invalid or has expired. Please reload the form and check that your cookies are enabled.” I have tried it from Foxfire and from IE 8, with the same results.

what is a short cut way of getting access again. I have FTP and PHPmyadmin access. I don’t have any data that’s particularly valuable so would it be best just to delete this install and reinstall it again or what?