Qextserialport comm. error

[simonCpp]

Hey,

I'm experiencing a very weird and annoying problem. While I record the data and I minimize or maximize the SW window I got corrupted data.

BUT, If I first open the RealTerm and then open / close the port and then starting to record data with my SW then the problem is gone.

P.S. it's happened in high rate - 400hz.

Any suggestions?
@
port = new QextSerialPort(portName,QextSerialPort::EventDriven);

if(!port->open(QIODevice::ReadOnly )) 
    return -1;

connect( port, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
port->setBaudRate(BAUD691200);
port->setDataBits(DATA_8);
port->setParity(PAR_NONE);
port->setStopBits(STOP_1);
port->setFlowControl (FLOW_OFF);
port->setRts( true );
port->setDtr( true );

@
My setup:
Windows xp sp3
Serial port RS-422
BaudRate : 691200
Qt 4.7.0
Qextserialport 1.2 beata2.