You know, my family's been having a similar problem with our pug. We got her about a month and a half ago, and she was fine for a while...she's a little over a year old so she was already housebroken. But then she quit going to the bathroom outside (especially at night), and instead started going in our upstairs bathroom...and
not in the toilet.
She will come "tell" us when she needs to go outside, but she just won't use the bathroom out there...she circles the yard once and then runs back to the door. I'm starting to think she's scared of the dark or something. The other night my mom was out there for 15 to 20 minutes trying to get that stupid dog to go. What's up with this? Neither of our other dogs act that way.