Please TEST these queries before running them on a live site! I do not want to be held responsible if something goes wrong ;)
Here is how a colleague explained his situation (the solution follows):
The trap is that if you create a content type and don’t remember to set comments off, all the nodes you create have to be updated manually to turn it off, even after you change the default in the content type settings. In our case, I imported a ton of records, and only later realized comments were on.
Well, you've probably all had a White Screen Of Death a time or two while dealing with Drupal or PHP. They can be very frustrating, but are usually easy enough to resolve. The following illustrates how to recover from a Drupal WSOD as a result of making changes to your cache settings in the Site Configuration -> Performance admin page. Again, this "fix" should only be applied if you have issues that you know are related to recently altering the cache/aggregation/compression settings.