Facebook is notorious for its frequent API changes. However, some error codes are rather persistent, in this case error 100: “next is not owned by the application”. I got it for the stream.publish popup (only in IE8, Chrome and Firefox work fine). You will find tons of suggestions that all tell you to change settings long removed by Facebook. So, here is a pointer: try setting the “Site Domain” on the “Web Site” tab to a meaningful value. This solved the issue for me, on Oct 13, 2010.And a more general pointer: when Facebook tells you that a setting is optional and defaults to something, it can still help to add some value. Most likely the “defaults” was true some time ago, but no longer is.