When I first installed it the first house I played the mailbox, dresser, and one of my sims along with the chair and book they were reading all disappeared. Poof. No I didn't do it accidentally. I was just sitting there and they disappeared. After I restarted, my sim reappeared but nothing else did.
Also, it seems like it takes my adult sims a long time to have a baby now. The first time I had this one couple try it took 3 times. Which isn't that strange, but I don't think it's ever happened to me. Then the next time I wanted them to have another kid it took 5-6 times which I thought was very odd. It usually takes 1 time. But since I installed InTeen it takes so many more. Also, aren't they supposed to be able to get pregnant from regular woohoo which I have yet to have happen yet.
And I can't get my teens to move in together. The first time I tried to do it, it worked but now the option won't even show up. They can go steady and get engaged but they can't get married or move in. I have the same problem with adult/teen relationships. Yes, I have their relationships where they should be. And I only have Sims 2 base game just so you know.