You may want to email support@lansweeper.com for an official answer, but... i'm curious now...
since you can edit the DB, i'm wondering if the below will allow both assets (it works on network assets with duplicate MACS on interfaces) - so should work here...
INSERT INTO tsysMacBlacklist (Mac, Comment) VALUES ('00:00:00:00:00:00', 'Whatever Comment Here')
GO
UPDATE tsysupdate SET MacBlacklist = GETDATE()
GO
Just remove the record if it doesn't work