Microsoft generally does a pretty good job at testing patches before they are released, making Patch Tuesday pretty effortless (except for the persistent need to reboot servers — wish they’d adopt a method like Linux where we could just restart the affected service after the update is installed).
But this month was different. I applied the July 2013 patches first to a development system and no issues were reported. So a few days later I pushed them out to production only to find the .Net Framework was broken; every managed procedure/trigger failed with the infamous .Net “Object reference not found” error.
It took me a while to pin down the problem. It was caused by MS13-052 (KB2840628). Uninstalling that patch and rebooting fixed the errors.
Microsoft mentions the problem in a related document and they mention a workaround in scenario 2.