Help! Outlook BCM Error: can't connect to database engine

[Peter Judge]

The business contacts and accounts contacts are not accessible. BCM is
unable to connect to the database engine.

How can I resolve this problem?

In anticipation of a re-install I'm trying to copy my BCM database files for
backup.

What are the significance of the files ending with:
..ldf; .mdf; and.msbcm?

THanks,

Peter