[Plugin: Achievements for BuddyPress] Can't "Change Picture"

The plugin works perfectly…until I try to change the image for an achievement. I see the images to select – no problem – but clicking on one does nothing, and then clicking on “Update” just refreshes the page. This message appears: “The Achievement’s picture has been updated.” But nothing has really been changed. I would be very grateful for some help here. Even a way to “manually” go in and set the images for achievements would be a great help. Thanks.

http://wordpress.org/extend/plugins/achievements/