After some automatic Windows updates, I was unable to open my SSIS projects in Microsoft Visual Studio 2012.
The following error was shown: The type initializer for ‘Microsoft.DataTransformationServices.Project.SharedIcons’ threw an exception.
After a google search, I found the following solution at:
Download and install http://support.microsoft.com/kb/2861107
(The hotfix is 780MB, say what?!)