White screen "Proudly powered by wordpress"

I have been having issues off and on with my site Since Thursday (3 days). I have never had any trouble viewing my site but I have been getting reports from others saying that they are getting a white screen with the error message “proudly powered by wordpress, wordpress twenty twelve child theme”. I contacted blue host and talked with them for an hour and they couldn’t find anything wrong. Then, I made sure that everything on my site was updated, as I hadn’t previously updated to 4.0 or updated my theme, that made no difference as I was still getting reports of it not working. Then, I deactivated all of my plugins and reactivated them one by one while my husband reloaded the page (he was having trouble viewing the site) and that helped it start working briefly but without making any changes it stopped working again. I don’t know what else to do. It is happening so intermittently that I feel like it has to be a server issue, but they say they can’t find anything wrong.