catalog corruption causes

I am trying to get my head around what causes catalog corruption.  I
have posted before with regard to recovering from corruptions (if that
is what indeed happened to me), and was given much help.

Does anyone know why a database catalog will get corrupted?  As I
mentioned previously, my db involves considerable use of temporary
tables created by php-psql connections.  Other than that, I don't know
of too much that is "odd" about my use (misuse) of the database.

Thanks,
r.b.

Robert W. Burgholzer
Surface Water Modeler
Office of Water Supply and Planning
Virginia Department of Environmental Quality
rwburgholzer@deq.virginia.gov
804-698-4405
Open Source Modeling Tools:
http://sourceforge.net/projects/npsource/