I took a look at your site and account. The issue is the ad size restrictions on your sidebar1 Zone. The ad size restrictions for a Zone really only work for image ads. Your slide in ad doesn't meet the size requirements (since it isn't a simple image ad) and is kept out of the Zone. To fix, remove the values from the Min Width, Max Width, Min Height, Max Height fields on your sidebar1 Zone.
Alternatively, you could create a second Zone for targeting some of the more sophisticated formats such as slide-in, dialog, interstitial etc. We usually call it something like "Utility Zone" and leave the size restrictions off. We put it on every page and then control what ads show on what pages using AdPlugg's Page Targeting features.