Well, you haven't really given much information on what's happening here.
Make sure the ESPs are checked in the Data Files screen in the launcher.
If that doesn't work, verify the files.
Perhaps you can clarify exactly what more information is needed. The ESPs are checked, as I would imagine they would have to be in order for any of the high-res textures to be displaying properly. Other than that I don't know what to tell you - some textures are still the original low-res textures, and a handful of them aren't working properly at all.
What I would like to know is how to start all over with the high-res textures. Steam doesn't seem to easily facilitate this. When I visit the DLC page in Steam, it just says that I have the textures already and I can play the game. No uninstall option, re-download option, re-install, anything. Hence my problem.