Well you'd load it up in FO3Edit and find out what and why and how the mod changed the greeting dialog. Dialog in FO3 is convuluted to say the least and when trying to change or add dialog to NPC's it is easy to add or leave unintentional changes in the mod.
But we need more information. Is that the only mod your using? Is it the only one you recently installed?
We need you to post your load order and the name of the mod in order to help you.