Yeah DrewsBrew. Same for me. Even if I don't load any mods, Oblivion will not launch from NMM. Application load error 5:0000065434. However, I have just realised that even though I can't launch from NMM, if I activate the mod with NMM, then launch normally from steam, it all works. I worked this out from a tip that came up when I was trying OBMM as well.