[Plugin: WordPress Navigation List Plugin NAVT] Blank items in NAVT list

I have migrated a wordpress site to a new server, which was successfully running NAVT.

After migrating to the new server I can no longer attach new posts to my navigation groups, but can still attach the posts which were created prior to the migration.

When I try to add a new post, it appears to have attached, but when the page is refreshed the item is blank.

Can anyone shed any light on this?!