I had the same Problem aswell.
Apperently Lansweeper changed the structure for the IPLocations, and each asset has a direkt connection to a asset group.
If the assets are scanned again this will automatically be corrected, but for assets that hasn't been scanned since the update they will now show up under "undefined location".
You can easily adjust this if you got to Configuration/Asset Group, edit the Location Info and just press OK. All Assets (for this location) will then be reassigned.
Peter