I have close to the same issue (I can get into my admin area but it is slow loading and timing out) and I got the advice to try to log in using different browser. And also to deactivate plugins to see if they were the cause. But you may have done that already since you deleted the themes.
I was able to get into my admin area using Firefox (for some reason)but load time are still extreme to the point of timing out sometimes.
I deactivated all plugins, same problem.
I have spoken to hosting (godaddy) but it working fine on their end. I have checked my broadband connection. Everything is fine – except wordpress.
