I recently performed a migration to SharePoint 2010 from MOSS 2007 using the database attach method. When performing a people search from my migrated site collection I was receiving "Property doesn't exist or is used in a manner inconsistent with schema settings" and not receiving any People results.
I created a new search centre on a new site collection as a test and it worked ok so it meant that people search on the farm was working but there was obviously something peculiar about the migrated site collection. The solution in the end was to edit the People Core Result Web Part on the search results page and expand the “Display properties” and make sure “Use Location Visualization” is checked.
I eventually found the answer here: