I had this weird problem with WordPress searches: in one of my blogs I couldn’t get any search results in the Edit Posts listing. Not even a simple search for the letter ‘a’ would yield anything. I tracked the cause down to the Search Everything plugin, and then began comparing what was different between the problematic blog and one that didn’t have this problem. Here’s where it got weird: there were no differences. The other blog is for testing only, so I could set it identical to the one with the problem, and still the searches worked consistently in the testing blog while in the other one they didn’t.
I tried unsetting Search Everything’s options and the searches began to work in the problematic blog too. So I tried setting them back on one by one… until I had them all as they had initially been, and the searches still worked!
There must have been some kind of a screw-up with the plugin’s settings, perhaps brought on by an upgrade.