I have a website that is finished and uploaded, at first it works fine but after a while it stops working.

By stops working I mean whatever page I go to just shows a blank page, empty source.

In Chrome though, I get `HTTP Error 500 (Internal Server Error)`

To fix this all I need to do is change debug to 2, refresh and then change it back to 0.

I do not know what triggers this to happen, I have tried clearing the cache folders.

There are no log entries in /app/tmp/logs/error from the last week.

Any ideas would be great. Thanks.