If you have had Visual Studio 2005 beta 1 installed and then removed it and installed VS 2005 beta 2, you may see an error like this when you try to set project properties in the VS IDE:
This can be resolved by running the VS 2005 beta cleanup tool.
The root cause of this issue is the issue I describe in this blog item. The VS 2005 beta 1 version of the assembly named Microsoft.VisualStudio.Shell.Interop.8.0.dll is being orphaned in the GAC after beta 1 is uninstalled. Then beta 2 installs a copy of the same assembly to a different location because the ProcessorArchitecture value for this assembly was changed between beta 1 and beta 2. For some reason the VS IDE loads the old version from the GAC even if the newer one is present.