Mildew/old person smell in house question?

Okay, so about 2 months ago, my boyfriend took down all of our old wallpaper form 35 years ago, primered and painted. The past month we have this smell coming from somewhere, and we can not figure it out. What can I do to get rid of this odor? It is only in the upstairs of our house where the wallpaper was. It is not mold, we had a home inspection in June 08 when we bought the house. We have boiler heat, it is not the furnace. Any suggestions thought Please this is driving me nuts!