Error: The database must be online to have a database snapshot

I have created one Mirror DB ('QuestMirror') for the principal one. This is in Restoring mode now.
Now I want to get snap shot (SnapshotDatabase) for this Mirror and I write my query like below:CREATE
DATABASE SnapshotDatabaseON(
NAME = 'QuestMirror', FILENAME = 'Drogram FilesMicrosoft SQL ServerMSSQL.1MSSQLDataMySNAPSHOT.mdf')
AS SNAPSHOT OF QuestMirrorThe error is : "Msg 1822, Level 16, State 1, Line 1
The database must be online to have a database snapshot."
-------------------------[:'(] How can make this online?

Is it Enterprise Edition of SQL Server 2005? Need that for snapshots.

Yes. Please note that I am creating the snapshot on the mirror DB.
Regards,
Ashish

Your syntax looks correct. Is mirroring established and synchronised?

Yes the mirroring is established and synchronized.

We do this on a mirrored database without any problems. I'll look up the code we use to create them and check, and I'll get back to you.

Mine looks like this

CREATE DATABASE db_dbss_0931 ON
( NAME = N'db_DATA', FILENAME = 'H:MSSQLDatadb_Data_Data_0931.ss'),
( NAME = N'db_INDEX', FILENAME = 'I:MSSQLIndexdb_Data_Index_0931.ss'),
( NAME = N'db_STATIC', FILENAME = 'H:MSSQLDatadb_Data_Static_0931.ss')
AS SNAPSHOT OF db

So... can't see what is wrong with yours, I'm afraid..!?

Thanks Thomas for your comments. I shall set up the quorum again from scratch and let you know. Latest is the same error .