I have my adsense code in an ad widget. There is a header ad, and two ads in the side bar. For some reason the header ad appears on every single page, but the two side bar ads have magically disappeared off of a few post. 90% of my post have all ads working, however there are a few where the ads in the side bar do not show up anymore, but the header and the link unit ads within the post still show up. Any idea what the issue could be? The technical support on the adsense forums is pretty lack luster.
SOLVED-- Well I found out the problem. For some odd reason Google has some serious issues with counting the ads on your post. The max is 3 display/text, and 3 link unit ads per page. I have 3 display ads on every page, and 2-3 link unit ads per page. For some reason on random post of mine Google would count a link unit ad as a display ad. Upon doing so it would remove a display ad from my side bar for every link unit ad that I included in my post. When I removed the code for the link unit ad in my post, the display ads started to reappear.
This seems to be an issue with Google when reusing code for link units. I use the exact same link unit code on every page which ended up causing errors in my ad unit count. To fix the issue I created a new link unit and added the new code to the page, now all 3 display units as well as all we link unit ads appear on each page. I guess I am going to have to make a new link unit ad for every few post and Google doesnt seem to like it when I reuse the code 30 times or so.