This was with NO mods after a reformat, clean install of windows.
It crashes when I speak to the dude and tell him I'm carrying less than 50lb, and agree to go.
Hmmm... http://www.gamesas.com/index.php?/topic/1183081-having-trouble-after-downloading-honest-hearts/ follow that link and as you have evidently followed the main instructions, delete your INI files first. They should be here:
\Documents\My Games\FalloutNV
Delete "FALLOUT" and "Falloutprefs"
Otherwise, I am not sure what else to do and I am not sure of the best way to contact Bethesda.