This morning I noticed that my test SharePoint 2010 installation was not working. Browsing to the site got me HTTP Error 503. The service is unavailable.
The problem seems to be related to the update KB2553365 which I noticed had been installed last night, following an initial failure.
Note this point in the description of the update:
After you install this security update on all SharePoint servers, you will have to run the PSconfig tool to complete the installation. For more information about how to use the PSconfig tool, visit the following TechNet webpage:
In other words, if your server is set up update automatically, this update breaks SharePoint until you manually run the PSconfig utility which applies SharePoint updates.
Further, there is no automatic notification of this requirement. You have to figure it out.
SharePoint administrators know about PSconfig, but companies with Small Business Server or other small-scale environments are not always familiar with the problem.
Worse still, in my case PSconfig has not fixed it. I am restoring last night’s backup.