Site not working

Try:
– switching to the default theme by renaming your current theme’s folder inside wp-content/themes and adding “-old” to the end of the folder name using FTP or whatever file management application your host provides.

– resetting the plugins folder by FTP or phpMyAdmin.

– re-uploading all files & folders – except the wp-content folder and the wp-config.php & root .htaccess files – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.

Well we are still having this issue with the website (https://trane-gnp.com/)
After doing the WordPress update to 3.9.1 it works anywhere from 3 minutes to 3 hours, and then it goes blank again. The Index.php file seems to go from 418 bytes to 0 (not sure what is doing this).

Here is what I have done so far with no solution:

All plugin’s disabled.
Plugin’s folder Renamed in FTP.
Manually updated WordPress to 3.9.1 via FTP. Deleted everything except for wp-content and did a fresh install.
Contacted the host (Intermedia.net) and they couldn’t come up with a fix or any problems on their end.

If I re-install the update and turn the Paid Ovid Theme OFF, the problem seems to be resolved (tested for 24 hours). I have contacted the designers of the website and apparently they were hands off in 2012, and in order for them to take a look/reinstall the original theme I need to pay $$.

I can attach the apache access and error logs if that will help.

Anything you can think of to help would be appreciated.