Perhaps this is a known bug or "feature", but I have not found any information. Just to report that searching the database with a word that includes non-ascii characters fails to produce any result.
In my database that should find at least 4 publications, but finds none.
This is true whether I search with the word on its own or using a particular field (in this case "author")
I'm on JabRef version 2.9.1 on a OSX (10.6.8)