Multiple primary key errors

I am rewriting my Rekall forms in OOo Base and am having a problem 
changing table primary key names.  After editing the name and hitting 
the save icon, I get:

    Error while saving table design
    Multiple primary key defined.
    [OK]

I am trying to change primary key names in several of my tables to a 
name that is more accurate and unique.  Closing and re-editing the 
failed table shows the new key name took, but the key icon is missing.  
If I try to reinstate the primary key by right-clicking the far left 
column on the key row and selecting "Primary Key", I get the same error 
when I try to save it and it is still missing if I close and re-edit again.

Yesterday, I was able to make these name changes on my main tables 
without any complaints.  Today, it is failing on my tables containing 
selections for the data entry form drop-down controls.  I tried going 
back and changing the key in a table that worked yesterday and it still 
worked.  I am at a loss to know the difference between these tables.

I did a web search for this error but did not find anything useful.
I did read something in a hit about "dropping" a primary key before 
changing it, but I didn't read anything about this procedure in the Base 
options, help, or guides.

Using:
Linux OO.o 2.4.1
mysql-connector-java-5.1.12
MySQL    5.0.84

Yes, 2.4.1 is old, but it is stable and after an OS upgrade which broke 
my stable Rekall database client, I am trying to get things working with 
Base first, before adding more unknowns with an upgrade to OO.o 3.x.

Any ideas?
Thanks in advance.
Girvin Herr