I recently uploaded a bad theme to my wordpress blog which resulted in my seeing a blank login page and index. I was unable to login in from my domain control panel to switch themes and I couldnt see my index.php page. I had to remove all files from the bad theme from my domain. After talking with my provider support person who uploaded a couple of PHP files to my wordpress directory, those files worked ok- I was able to see them on my domain. So my wordpress directory was not corrupted. As far as I knew only my bad theme files, my index.php and wp-login.php were blank and corrupted.
I imported my good wordpress files from my PC (which were downloaded to my PC upon creation of my wordpress blog) and uploaded them to my wordpress directory to replentish my wordpress folder and files. After getting back into my wordpress I made a backup of my wordpress folder and files.
If you are experiencing these problems let me know if you have any other questions!
Steve