Full-text indexes on nonpersisted, computed columns are not allowed
You cannot create full-text indexes on nondeterministic and imprecise computed columns. Such columns cannot be used as type columns or as full-text key columns.
In SQL Server 2000, a full-text index can be created by using a nondeterministic and imprecise computed column as the type column or the full-text key column. This functionality is not supported. When you upgrade, older, incompatible, and unsupported full-text indexes are disabled.
To enable these full-text indexes, modify the column definitions so that the columns are deterministic and precise.