There is the setting within your .cfg file to turn on flocking:

# Use file locking (1 = Yes, 0 = No). Should be used, but won't work on Win95.
$db_use_flock = 1;

I can see the large database getting corrupted with being so large, but I'm curious did you loose data during the process of adding records as admin? I found out several months ago that on one of the servers I use that If I have javascript turned on in my browser and try adding or modifying a record for some odd reason it would wipe out the database.

If I turn off javascript in my browser (which I usually do when surfing) I have no problems.

It would be interesting to hear if anyone else has had the same problems. I tend to think it caused by the poor formatting for the advertising banners that causes the problem in my case??

Unoffical DBMan FAQ

http://creativecomputingweb.com/dbman/index.shtml/