One of our content editors was trying to save a document and the below (see image below) error caused a 503 error and brought my website down completely. I had to do a iisreset from a dos prompt to get the site working again. How can I fix this problem and prevent it from happening in the future.

I also posted this same request out on https://umbraco.zendesk.com/requests/8034 but never got a response.  Is that the wrong place to post questions for support?