Ok, after digging around some more I found a solution that works.
After installing IronPython Studio I can no longer open WPF projects (.csproj) in Visual Studio 2008.
The error associated with this is:
The project file ‘PATH TO THE PROJECT’ cannot be opened.
The project type is not supported by this installation.
The solution -
Execute the following command in a run dialog:
After running this command I was once again able to open my WPF projects.
My development environment (under which this error arose):
.Net 3.5 SP1 (and everything below that)
Visual Studio 2008
Visual Studio 2008 SP1
Microsoft Expression Blend 2.0
Microsoft Expression Blend 2.0 SP1
The only projects I couldn't open were WPF ones, regular .csproj files could still be opened in Visual Studio 2008.