Found it. Somehow the GlobalCache was returning values for Company (and maybe other items), but they weren't valid. May have been left over from first attempt. Anyway, temporarily, I changed APCWrapper.class.php to return false for isAvailable.
This whole mess may have been related to that I first installed using the InnoDB engine just to make sure the software ran ok on my server. I changed system_config_form.php to allow the IBM DB2 for i database engine, dropped my database, removed the config and re-installed. (This was the point of my "proof of concept".)
FYI, the only other items I needed to change (so far) to use the ibmdb2i storage engine was to change the empty_datetime values to '1000-01-01 00:00:00' because DB2 doesn't allow 0 and MySQL doesn't allow DB2's low value of '0001-01-01 00:00:00'. It'd be nice if nulls were used as a standard.
It'd be nice if the SQL statements to create the tables and populate them would use EMPTY_DATETIME instead of constants.
--Bryan
If anybody understands the cache well enough to let me know how to clear it, maybe I can enable it again.