Open XML SDK: Does the runtime version matter? YES!
There was a discussion in the Open XML SDK forum today that I found interesting. Certain namespaces for Office 2010 weren’t being recognized with a reference to the Open XML SDK version 2.0, even though they should have been. The references were being picked up just fine with a reference to the newer Open XML SDK 2.5, however.
When I tested I had no problems using the namespaces. Luckily, I thought to include the version number of the Open XML SDK runtime in my reply. Turns out that Microsoft replaced the original download with a newer version without any public notification, either about the fact that it was being done or mention about problems with the older version. When the OP downloaded the newer version, the problem disappeared!
So if you need to use the older version of the Open XML SDK and are having problems with any namespaces that belong to DocumentFormat.OpenXml.Office2010.Word.DrawingShape, try uninstalling, downloading a newer version and re-installing. You need a version that starts with v2.0.5###; the problem was ocurring in v2.0.4###.