Another possible issue/solution, probably under possibility 1:

I get a lot of SAN detatch errors from a certain iSCSI SAN. The SAN Drives will drop, and reattach. Fortunately, the Windows OS sees the drives as being back but once SQL Server looses the connection, there is no reconnect. These will show up as suspect databases (multiple). Solution so far (and I have been lucky) is simply restart the SQL Service. Usually shows up as a 9002 error in the error log.