It seems to me that there is a problem with data buffering being incorrectly set in both VFP5 and VFP6 under the following circumstances...

Create a base form class with Buffering set to Optimistic (1).
Create a form based on this class with buffering set to None (0)
Add any old .dbf to the dataenvironment.
Put a button on the form which does...
wait window str(cursorgetprop('Buffering', 'the .dbf alias goes here'))
Fire up the form and you will see the the buffering is (incorrectly) set to 3, optimistic row.

Now set autoopentables to .F. in the DE. and put
thisform.dataenvironment.opentables()
in the load event of the form. The table will now be opened in the load event and in this case the buffering is correctly set to 0, none.

The work around is to explicitly set the buffering for every cursor in the dataenvironment.

It seems that the DE is using the buffering mode of the class of the form when it opens tables prior to the load event of the form.