I have looked over the FAQ, still stuck. I'm currently checking to see if any other elements on my pages are prohibitting the ads from displaying. Seems if that were the case though the ads would not display at all instead of sometimes rendering ads and sometimes not..
I have also tried serving the ads from file, rather than from the database. Still no luck.
Maintenance shows the database and installation are error free.
UPDATE: I've discovered that the normal Javascript invocation tag works fine but asynchronous will still, at times, not display ads.