Message set in QMessageBox not displayed

[VIAlina]

Hello, as this is my first post i`d like to first thank you all for the help I have found in other forum posts in the past :)
Now for my question...
I have the following code bit:
@processing.setWindowTitle ( "Processing" );
processing.setIcon(QMessageBox::Information);
processing.setText("The file is being processed. Please wait!");
processing.show();
compare (item, item2);
processing.hide ();@

For some reason, it shows the window with its title, but it appears blank and I dont get why.
When I call processing.exec(); instead, it appears just fine. But I can`t use it as i need control back to the application right away.

Any ideas?