I know you're saying that you're seeing a 'film of paste' on the TOP of your wallpaper but are you sure of this? Could it be on the UNDERSIDE? Could it be a stain?
W/O knowing the details of how you hung the paper (including the materials), it's hard to say what happened. IF you happen to know the mfgr of the paper, ctc them for advice. And be sure to provide them with the details of the job (which you left off your post here), for them to evaluate. I'm sure they can help.