MS13-052 Causes issues with SharePoint15 Jul 2013 | SharePoint 2010
Update 7/25/2013: KB2872441 will resolve this issue.
Thanks to @kelvin_hoyle for pointing this one out, the .NET Security patch MS13-052 is causing issues with SharePoint. For now, it is recommended to not deploy MS13-052 to SharePoint servers. See this TechNet thread for further details.