Update attempts freezing in clerk

[Barry Wiseman]

filePro 5.0.14
openSUSE 10.3

This busy (typically 50+ users) site is experiencing some intermittent 
event whereby attempts at write access to their main file cause the 
session to freeze.  It is happening several times a week.  They 
typically experience this when selecting an "Add Records" choice (-xa) 
from their main menu.  The screen clears, the -h text draws, and there 
she sits.

At those moments, I find the following: I enter the problem file like this:

     dclerk 3disp -s1 -y - -z -

I can navigate through records without a problem.  But when I press "U" 
at any record, the session freezes, does not respond to BREAK or QUIT. I 
must do a kill -9 from a different session to regain control.

I have them contacting me immediately each time this event occurs. 
Sometimes the condition is quickly self-clearing (by the time I log in 
to their box the event is over); most often it persists long enough for 
me to study.

By the time I'm looking at it there are usually several or more Add 
Records sessions running against this file, all apparently frozen.  I 
usually do a "kill -9" against these sessions one by one; during this 
procedure the condition usually clears, but I'm unconvinced that my 
kill's are the reason, since it also sometimes goes away when I've done 
nothing.

During these events showlock does not report any unexpected locks (I 
check key, data, indexes, map and lockfile).  I have sometimes found 
several zombie freechain processes, but I think that's a red herring.

Ideas?