Please try to do the following
1.) log in to www.bitbucket.org using the "log in"-button using the browser Epiphany. I used the version 2.30.6. Then close the browser window without logging out.
2.) Log in to www.bitbucket.org using the "log in"-button using Firefox 14.0.1 and then log out using the "Log out"-button in the drop-down list for your username.
3.) Open Epiphany again and begin typing in https://www.bitbucket.org . It should offer you an autocomplition for this. Accept the offer and load the site.
When I did this, I landed on my dashboard again. Why is that? By "logging in" using Firefox and logging out, I should have invalidated the cookies, I used during my "log in" using Epiphany. Therefore Epiphany should have taken me to the log in-site.