Problem: When I opened NMM, chose FNV, I'd get an error that Install Log Not Upgraded. The details button told me that the install log was referring to a mod that was no longer installed.
Solution: I went to C;/Games/FalloutNV/Install info. Then, I closed my eyes and deleted the installlog.xml. Voila, NMM created a new one and opened the FNV section, and there were all my mods.
Whew. BTW, Skyrim, Oblivion, FO3, and FNV all work great with NMM. Thank you!
Edited by AbleGnome, 01 January 2012 - 05:48 PM.