THE PROBLEM IS SOLVED. I DUNNO HOW TO CLOSE THIS QUESTION. ANOTHER SERVICE IS PROPABLY RUNNING AT ALMOST SAME SYNC THAT DOES THE THING. MY WORK "MATE" WILL HEAR A THING OR TWO IN THE MORNING.

I have following code in windows service: data is in the dataset and it has been populated earlier and then rows are updated and inserted to dataset tables before calling code below.

using (dataSetTxn = _cnctn.BeginTransaction())
{
    try
    {
        _somePlanAdptr.UpdateCommand.Transaction = dataSetTxn;
        _someLogAdptr.InsertCommand.Transaction = dataSetTxn;
        _someLinkAdptr.InsertCommand.Transaction = dataSetTxn;
        _someDataAdptr.InsertCommand.Transaction = dataSetTxn;

        _log.WriteDebug("Updating SomePlanAction");
        _somePlanAdptr.Update(_ofDataSet, "SomePlanAction");

        _log.WriteDebug(string.Format("Inserting {0} rows to SomeLog")); //error
        _someLogAdptr.Update(_ofDataSet, "SomeLog"); 

        _log.WriteDebug(string.Format("Updating SomeLink with {0} rows", _ofDataSet.Tables["SomeLink"].Rows.Count));
        _someLinkAdptr.Update(_ofDataSet, "SomeLink");

        _log.WriteDebug(string.Format("Updating SomeData with {0} rows", _ofDataSet.Tables["SomeData"].Rows.Count));
        _someDataAdptr.Update(_ofDataSet, "SomeData");

        _log.WriteDebug("Commiting all changes to database.");
        dataSetTxn.Commit();
    }
    catch (Exception e)
    {
        _log.WriteError("Updating database failed -> rollback", e);
        if (dataSetTxn != null && _cnctn.State == ConnectionState.Open)
            dataSetTxn.Rollback();

        throw e;
    }
}

so one of the lines causes an exception

log.WriteDebug(string.Format("Inserting {0} rows to SomeLog")); //error

still the first adapter's data is updated to database. when debugged the data is not yet updated until the method that calls all (including this bit) exits. The method that does all is timed with System.Threading.Timer.

Thanks & BR -Matti