I'm also experiencing this problem with my sim that lives in Strangerville. Are the NPCs here not date-able because of the possibility of infection? Just a thought. I'm having trouble with Jess Sigworth (infected), Erwin Preis (not infected, manager of the curio shop), and Don Lothario (not infected, nonresident, but bartender at 8 Bells.)
I have successfully dated Sims from StrangerVille as recently as today, including Jess Sigworth, Meredith Roswell, Alice Martin, and Leslie Holland. Gold dates for all of them. I think Jess and Meredith are currently infected but that hasn't been a problem.
I found my problem, don't know if it will help anyone else, but just in case...
The sim trying to date was an alien (from GTW) and I had used MCC to add the "hidden_isalienpolinator" trait. I thought this would enable her to impregnate a male and have a full alien baby, but it didn't. What it DID do (apparently) was to signal the game that she was a hidden NPC, and ineligible for most, if not all social events. It was as if she wasn't there at all. When I removed the trait, everything went back to normal, or as normal as things get in Strangerville, anyway.
