too many Fatal Error 1: shutdown messages

Running PostgreSQL 7.2.1 on RedHat Linux 7.2

Over the past few days, the database has been acting
strange and have been trying to shutdown. While my
postmaster is running debug level 2, when I check my
logs to see why, I get :

[snip from log]

Jan 8 09:54:16 test_srv postgres[19069]: [12354] FATAL 1:
The database system is shutting down

[/snip from log]

There doesn't seem to be any rhyme or reason for it;
yesterday, I thought it was one of the drives having
problems and the kernel gave an error.

Last night, I thought it was because of too many
users logging in (it had reached it's max and gave that
message).

Both seem to be red herrings.

I'm going to expand on the debug level to see the whys and
hows of some of these things, but, I'm running out of ideas.

Any suggestions?

-X