" First of all, are you advertising in both the search network and the content network? Do you know where your conversions are coming from? Search? Content? Both?"
I've been getting conversions from both so have been using both. I've had problems in the past with bad clicks when I use all countries so I have specifically limited searches to Europe and the US and have gotten good response on Content from that.
"If they were coming from Content, then run a placement report and see if you can spot which site(s) were providing them - something may have changed with that site - they could have more ads competing, or gotten rid of adsense, or changed their layout - any number of things."
That's what is weird. The clicks completely stopped on both the content and from Google even though the impressions stayed the same.
"If they were coming from search - do you still see your ads on the first page of Google when you search on one of your keywords? Do you have any new competitors?"
I'm a bit limited here. I'm currently living in a country that I have blocked so I can't see my ads at all.
"Have you checked your quality scores? Have they dropped recently?"
This is also a bit of a problem since I have changed all my ads over the past year and lost quality score as a result even though my ads are now better optimized. Thus, I can't really get a good comparison with what I was doing a year ago.
I'm going to run the reports you mentioned and see what I come up with. Thanks. That's a huge help.