Citrix has released yesterday a KB article stating the following regarding ICA and RDP connections failures after applying patch MS12-024.
When you apply Microsoft patch MS12-024 on a Windows Server 2003-based Terminal Server, Independent Computing Architecture (ICA) and Remote Desktop Protocol (RDP) connections fail.
This is a known issue with Microsoft Windows 2003.
Background
Microsoft released a patch on April 10, 2012 to address a security vulnerability issue with the operating system potentially allowing a remote code execution.
To review the information refer to http://support.microsoft.com/kb/2653956.
If you install this patch, you might experience an issue that ICA and RDP connections terminate on the server.
Resolution
To correct the issue you can install the Microsoft Hotfix 938759 available at http://support.microsoft.com/kb/958476.
You can read the complete article here.
Last Tuesday Microsoft has released a critical hotfix affecting Remote Desktop Services for versions of Windows commonly used as part XenDesktop and XenApp environments. Microsoft is strongly recommending that customers apply this immediately.
This security update resolves two privately reported vulnerabilities in the Remote Desktop Protocol. The more severe of these vulnerabilities could allow remote code execution if an attacker sends a sequence of specially crafted RDP packets to an affected system. By default, the Remote Desktop Protocol (RDP) is not enabled on any Windows operating system. Systems that do not have RDP enabled are not at risk.