>alter table 'System_Data' add foreign key tag 'cSdAdKey' references 'Address'
>validate database


I changed this to VALIDATE DATABASE and got the following error message:

Object #275 (Relation: Relation 1): can not find associated index referenced by this object. So the problem lies with that specific alter command. I also do not see the need to constantly reopen the database with a validate command. Just issue VALIDATE DATABASE. It may also help to troubleshoot this by opening the DB exclusively first.