Скорее всего, Ваша БД находится в состоянии "suspect". Для более детальной информации вывесите здесь errorlog вашего сервера, чтобы понять что с БД.
А так чтобы ее убить, выполните рекомендации из ErrorGuide


1.Log in as the "sa".
2.Check to make sure the database has been marked "suspect." The following query produces a list of all databases which are marked suspect:
1> select name from master..sysdatabases
2> where status & 320 = 320
3> go
3.If the database is marked "suspect", go to step 4. If it is not marked "suspect", mark it in one of the following ways:
a.Execute the sp_marksuspect stored procedure discussed under "How to Mark a Database "suspect'"", and restart Adaptive Server to initialize the change.
b.Use the procedure below:
1> sp_configure "allow updates", 1
2> go
1> use master
2> go
1> begin transaction
2> update sysdatabases set status = 320
3> where name = database_name
4> go
Verify that only one row was affected and commit the transaction:
1> commit transaction
2> go
Reset the allow updates option of sp_configure:
1> sp_configure "allow updates", 0
2> go
4.Shut down Adaptive Server with nowait:
1> shutdown with nowait
2> go
Restart the server to initialize the change.
5.Remove the database:
1> dbcc dbrepair(database_name,dropdb)
2> go