Lame_Wolf - 7:20 am on Oct 21, 2012 (gmt 0)
Totally untrue. If the old-style code is being used, then adverts will show up straight away. If the new-style code is being used, then about 10 minutes.
It takes awhile for Google to properly index your site which makes most of the ads not to show up.
I have a section on my site that used link units. A while back I notice a huge drop in earnings from that channel. On further inspection, there were no link units showing, at worse. At best, a few of the pages showed them, but only one link instead of four.
I looked at that section today, and now there are none showing. I have played with that page till the cows come home. (removed hotlinking js, removed links to other pages in that section, removed other text) and nothing worked.
When I renamed the html page to 0.html and uploaded it, the link units reappeared.
There are no obvious stop words in the URL either.
I did it to another page in the same section, and renamed that to 1.html and again, the link units appeared.