I have a similar issue only i get an error message. You are missing C:\program filers(x86)\steam\steamapps\downloading\22330\Data\Oblivion.esm but this is not my oblivion directory. i have no idea what this directory is for or where in the settings it is referenced, but copying the oblivion.esm file here got NMM open. still can't find a setting to fix this so i can delete it. i think maybe i first opened NMM while Oblivion was still downloading. Rescanning installed games didn't fix it.