Hey Brian,
The BI installer alone should never make a policy change to the sapadm account on the server.
Could it be that your domain policy is set to remove the "Log on as a service" from local accounts? My theory is that when you rebooted the server after doing the repair, upon restart, your domain policy was re-applied to the computer and stripped sapadm of this user right assignment and subsequently caused the SapHostControl service to fail.
Can you confirm if this is the case (maybe by rebooting the server and see if it breaks again?)
Regards
Toby