To everyone who has ever or will yet experience locking up their machine 
when trying to restart CDD after shelling out of an already active session, 
I have the solution.  After doing this very thing again on Monday, 
I set about to smarten up CDD.BAT.  Here is my revised version of CDD.BAT.  
(Note:  Don't forget to change the C:\CLARION3 path if yours is different!)  

Although LOCKFILE.SAV can have any text you want, here is what I used:

THIS IS THE LOCKFILE TO PREVENT MACHINE LOCKUP WHEN CDD ATTEMPTS TO LOAD 
WHILE ONE COPY IS ALREADY LOADED IN MEMORY.

I have tested this method in several different configs. with my machine
(a clone 486DX-33 with 4MB using DOS 6.2 and EMM386.EXE, etc.)
and it has worked correctly each time.

Hope this will prove of benefit to you.

Rick Smith
73223,704
Computer Visions & Technologies, Inc.
(803) 754-4433