This has come up twice now, so it seems to be worth posting in the hopes that folks will find it when searching for the error message.
Here's the scenario.
Ben Ryan, a developer on version control, describes the problem and the workaround as follows.
The root cause of the problem is that the CMS Service Pack that adds support for Visual Studio 2005 is built against a version of the Microsoft.VisualStudio.Shell.Interop.dll assembly that is incompatible with the version we ship with other products (i.e. VSIP 7.1 and VSIP 8.0). Therefore, the IVsHierarchy that Microsoft.ContentManagement.DeveloperTools.TeamExplorer subclasses cannot be cast to the IVsHierarchy that TFS references in its managed package. We are engaging the Content Management Server team to resolve this issue. In the meantime you can work around the issue by closing the solution and checking in from the Pending Changes toolwindow or by checking the files in from the command line.
The root cause of the problem is that the CMS Service Pack that adds support for Visual Studio 2005 is built against a version of the Microsoft.VisualStudio.Shell.Interop.dll assembly that is incompatible with the version we ship with other products (i.e. VSIP 7.1 and VSIP 8.0). Therefore, the IVsHierarchy that Microsoft.ContentManagement.DeveloperTools.TeamExplorer subclasses cannot be cast to the IVsHierarchy that TFS references in its managed package.
We are engaging the Content Management Server team to resolve this issue.
In the meantime you can work around the issue by closing the solution and checking in from the Pending Changes toolwindow or by checking the files in from the command line.