We got the following error when trying to validate a changeset
Cascade or Restrict Delete: field integrity exception: unknown (must specify either cascade delete or restrict delete for required lookup foreign key)
Anybody know how to resolve?
Expecting no error when validating
Sounds like missing element in the XML (maybe a tag that has to be specified now but your XML was generated with older API version)?
Post the definition of your new lookup field (you can see it in target org's "view source" in the inbound change set). Could it be that the cs was prepared in a winter release org last week but now the target is on spring? If the source is on spring now too you can simply clone the cs and reupload. If not... Hm, try creating the field manually in the target org