I had the same trouble after adding the cu extension editor. If you are like me you probably just added the extension editor and didn’t click on it again in the menu and select apply. The add button apparently does not apply the new rule too. After clicking the apply button I am experiencing the promised syntax highlighting.
Currently, I am with CUDA 3.2 + VS 2008
You should copy usertype.dat to this fold:
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE
It’s verified by testing.