When I try to activate the falloutnv.esm master in the data menu and click enter, nothing happens. When I open the data menu again everything else is checked except the falloutnv.esm. No matter how many times I check the falloutnv.esm box and click enter, it never loads it and it is always uncheck when I reopen the menu. Help!

Did you try that suggested in yesterdays thread "GECK not loading any files"?

Make sure you're using the latest version of the GECK. Try using this: http://fallout.gamesas.com/eng/downloads/geck.php