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.
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.
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.