FC3T1 - Prelink - System Hang every night c 04:30

[richard mullens <mullens ntlworld com>]

My system (Duron 850) hangs every night at about 04:30.
System doesn't respond to mouse movement, keystroke, Control alt 
anything or PING.

The time in the botton right hand of X display is the same as (or 1 
minute later than) the timestamp of /var/log/prelink.

(Frozen) top shows "makewhatis" and prelink running recently.

Last message in /var/log/prelink always (so far):-
"warning /usr/lib/lib???.so??? has undefined non-weak symbols.


This problem doesn't affect an other machine I have running FC3T1, and 
perhaps, tonight,
now that I have shut the case and added an extra fan, it will go away. 
However,I'd be interested
to know the purpose of this nightly activity - and the consequences were 
I to inhibit it.