Exchange 2010 message delivery issues due to low disk space

 my Exchange 2010 stopped delivering messages to one of the databases. All the messages are in the queue.

The error I am geting for the database is

431-4.3.1 STOREDRV; mailbox disk is full
431 4.3.1 STOREDRV.Deliver.Exception:StorageTransientException.MapiExceptionLowDatabaseLogDiskSpace;
Failed to process message due to a transient exception with message Cannot open mailbox /o=XXXXXX/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=XXXXXX/cn=Microsoft System Attendant.

I am kind of baflled because

My DB has 200 gb Disk space free and Logs have 200 gb free.

Your help will be appreciated.

Thanks

EagleAsh