Recently, I had the pleasure of troubleshooting several Error 3624 on a SQL Server 2008 R2 instance. It seems to be related to bulk copying in data to a principal database in a mirroring setup. The principal never runs into trouble, but the mirror database generates an error when trying to replay the transactions. It tries to initiate a lock escalation, but fails for some unknown reason. The mirroring session is then suspended, and will have to be reinitialized from start. From this Microsoft Knowledgebase article http://support.microsoft.com/kb/974319 it seems that this problem should be fixed in CU1 for SQL Server 2008 R2. But we got the exact same problem even though we were running on SP1 (10.50.2500). So it seems that this error might have resurfaced, or that there exists a similar bug still. If you run into this problem, with SP1 installed, you should contact Microsoft Support. In the meantime, two workarounds should be possible. Either do a regular insert instead of an Bulk Insert, or you can break mirror beforehand and reinit it after the bulk insert operation.
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