You can try deleting one of them, and then try to replace the dll in the project root (not the Assets/* folder). Base it on whether you run the 64-bit editor or not, maybe. I got it working by deleting the 32-bit one under Standard Assets/EyeX */lib, then (re)placing the 64-bit one in the root. Hope the same works for you.
I also was wondering if anyone has had similar problems with the second error message. My colleague/student friend is migrating his project from 4.6 free to U5 Personal. After handling the duplication issue, Unity still can’t load the correct library no matter where we place it. We even tried opening the exact same project with the exact same files on my editor/computer, which works fine.
Anyone have any troubleshooting tips for Tim and/or us here?
Not trying to hijack your thread, thought I should just post here since it’s the same issue. =)