ashdesigner on "Word "error" on white blank page"

Hello,

I'm stuck with a WP 3.7.1 (and also noticed on earlier versions) showing up just word "error" on a blank white page, which happens in unpredictable time periods. After a while (5-10 minutes), the website launches again.

I'm thinking of "Better WP Security" plugin as the issue, but might be mistaken. I also don't yet understand the connection between the "error" and the plugin settings (if I'm right), anyway.

Server logs don't show anything, as if it was a common http request.

Would much appreciate your help guys.