Thanks Joshua.
Any ideas what the numbers signify? Number of changes?
What is the recommended way forward now? Fix the unique constraint error then reverse (go from forum.name.com back to name.com, then back again) or do something else?
Edit: done
I entered the app and Rails console then deleted the TopicLink in question then went from forum.name.com back to name.com, then back again.
backup_metadata=1
categories=6
email_logs=318
email_tokens=2
groups=1
incoming_domains=3
incoming_emails=3
javascript_caches=4
post_custom_fields=277
post_revisions=140
posts=444
post_search_data=51
search_logs=10
site_settings=5
stylesheet_cache=564
theme_fields=9
theme_settings=3
topic_links=281
topics=30
topic_search_data=8
translation_overrides=1
uploads=54
user_auth_token_logs=48
user_emails=2
user_histories=189
Done