The problem could be several things, the tv, your cables, apartment cables, or just a poor source. More than likely its not your tv if OTA signals are fine. I would suggest upgrading your s-video cable to component first of all. That should make an improvement of some kind. Another option would be to get some kind of power/line conditioner that you could run the source cables and power cables through. This might clean up some of the interferance you're getting in the apartment. This could also offer surge protection too.
I'm not an expert on power conditioners, but I can tell you theres quite a few threads on this forum about them, so maybe check them out and see which one fits your budget.