no profile fields available since upgrade to 5.x-2.8

We recently upgraded from a very old version of User Imports (5.x-1.2-beta) to 5.x-2.8. Now the field match drop down lists are all blank and none of the other import fieldsets are visible on the form (see attached screenshot). I tried switching the admin theme back to garland but that didn't help. I tested the 6.x-1.2 version against a copy of the database and it works fine, so problem appears to be 5.x version of the module.