Is there a way to import a backup file rather than restoring it? Can you edit it from another server? Was it karma? Was there some sort of black magic in the air on June 20th, 2008 at 8:03pm? Do they know any Microsoft reps that may have been trying to get their business?
SQL backups aren't like file backups; a SQL backup is the set of SQL commands required to create the tables backed up and populate them with the data in them. Which is actually how I discovered the problem to begin with - because running the SQL commands necessary to get the data in there would produce errors.
You can't edit SQL data directly, either, from that server or any other. You process it with, again, SQL commands that would error out if you attempted to violate the key constraints.