CRM 4 : Lookup name label not being displayed
I've been using a tool called CRM View Layout replicator to copy the columns in one view to other views. It turns out there is a bug in this tool and when it updates the "lookup view" it updated the preview attribute in the customisation xml, it set it's value to 1 instead of keeping it's origin value of 0. When you select an entity form the lookup records dialog, the system uses the view where preview value is 0 to find the name of a selected entity and populate it in to the lookup on the form.
The fix is to export the entity xml and update preview="1" to preview="0" for all the lookup views (1 per entity) that the tool has been used against and then reimport the xml again.
Here's an example where the preview attribute is incorrect: