Using IBO 4.9.7, BCB6, Windows Vista, InterBase 2009.

I am porting an app using the VCL which was written for another
database system (NexusDB). There, it works well since years.

When I ported this to IBO using InterBase 2009, the basic functions
also work. This includes "simple" additions and updates of records,
whether framed by transactions or not.

However, on some action sequences, I get the VCL error
on updating records: "Datensatz wurde zum Aktualisieren nicht gefunden"
which translates like "Data record was not found for making-it-current".
The sequence is: Locate, Edit, Post. The Locate and the Edit are
successful, which I confirmed by tracing. The error occurs on Post.
Then, the same error rises on the following Commit, obviously leaving
the transaction open, which at last causes the discarding of all further
database actions executed done on the EXE file run.

(I use a single transaction object created on opening of the database,
paralleling the direct application of StartTransaction and Commit to
the database object as it is possible with the other database system.)

What went wrong?

Thanks for any help.
- Karl