In the posts section of the nexus page, there were a couple of mentions of conflicts with DC Interiors. One post suggested to either remove 2 of the guards from Reilly's Rangers mod, or remove Seward Square from the DC Interiors mod.
I haven't yet downloaded the DC mod, but I thought I'd take a look at the Ranger mod. WOW. There are about 6 errors that xEdit initially complains about, before xEdit is even finished loading the mod. Those errors basically refer to 6 instances of guards that had been placed in Seward Square. When I went to the Seward Worldspace to investigate, xEdit threw all kinds of errors anytime I moved my mouse over the records of the guards in question.
I don't know enough about NPC records to know WHY xEdit didn't like those guards, but I am curious. If anyone has a chance and takes a look at the mod, please let me know what was wrong with those guards! For now, I just removed them.