How do I log out of the WPMU DEV Dashboard plugin?

Hi, I installed WPMU Dev Dashboard plugin, but logged on with an old account that is no longer active. How do I log out of that account within the dashboard plugin so that I can log in with the correct credentials and access my account?

I've tried uninstalling the plugin, deleting the files, cleaning cookies and cache in browser, reinstalling the dashboard plugin, and it still automatically logs me in with the old account. I can't see a log out option.

Thanks
James