Search Returns No Results in User Email

I used to be able to easily search for messages with certain subjects in the Read User Mail Usermin module. Now, when I do a search, for example for the word "Spam" in the subject, it always returns 0 results, even if messages that should match are obviously there. Neither the basic Search box or the Advanced Search options return anything. Currently running Usermin development version 1.224.

Closed (fixed)