Ok good, one less possible thing to factor into the equation.
Do these steps and let me know the results:
Delete the .htaccess file in your website root folder and the .htaccess file in your wp-admin folder. Can you login to your website? Is the frontend and backend displaying normally?
If so, go to BPS Custom Code and cut (not copy) any custom .htaccess code that you have added to any Custom Code text boxes and save it to a Notepad text file on your computer.
Click the Save Root Custom Code button.
Go to the BPS Security Modes page, click the Create secure.htaccess File AutoMagic button and activate Root folder BulletProof Mode again.
Is your site still displaying correctly on the frontend and backend?