EOAdaptorChannel problem

Hi there

I'm using EOAdaptorChannel.deleteRowsDescribedByQualifier(EOQualifier,
EOEntity) to delete a big pile of rows with the deletes cascading to other
tables. I'm getting my adaptorChannel by doing this:

 EOEditingContext deleteEc = new EOEditingContext();
 EOAdaptorChannel ac =
((EODatabaseChannel)(EOUtilities.databaseContextForModelNamed(deleteEc,
"MyModel")).availableChannel()).adaptorChannel();

Sometimes (not always, never on my desktop box and only sometimes on the
development test server) deleteRowsDescribedByQualifier throws a
NullPointerException. If so, I catch it and use
adaptorChannel.adaptorContext().rollbackTransaction(), but that in turn
throws an IllegalStateException. On one occasion I also got a
"com.webobjects.jdbcadaptor.JDBCAdaptorException: Cannot
rollbackTransaction() while a fetch is in progress" instead of the
IllegalStateException.

Looking through the docs, it seems that "Some possible reasons for failure
are: * The adaptor channel isn't open. * The adaptor channel is in an
invalid state (for example, it's fetching). * An error occurs in the
database server."

So, I'm taking a guess that this is happening because the EOEditingContext
I'm starting with uses the same EOObjectStoreCoordinator as other
EOEditingContexts, and that if I just use a new EOObjectStoreCoordinator in
the initial new EOEditingContext constructor call, I might get round this
problem (leaving aside for the moment locking and integrity and all the
other issues). Could anybody tell me if they agree or disagree? Would I be
better just constructing "DELETE FROM ..." SQL and squirting that in, or
maybe even a stored procedure would be better as it could lock on db side
etc?

Thanks for any thoughts
Igor