@dwerty - might be a silly thing to check but it can be overlooked at times. Are you still the highest bidder for your targets? I'm often in fierce bidding competition with other members that I've hired someone to login every hour and overbid
@Povidon - if you haven't changed anything and just noticing a drop in conversions, think of it this way....you're presenting the same landers to the adware users, and probably showing it every 24 hrs (by default usually). So the users are seeing the same thing over and over. They get tired of seeing your offer, then start closing your pop-up/pop-under. This happens often to me and my theory is my ads get stale. I often change it up (freshen up the ad with a new layout or graphics). I usually stop a campaign after running them a week or two (sooner if conversions get super low). That's my opinion, anyway.