Architecture problem using threads, custom events and signals/slots

[jacek]

why should I use QDeepCopy in my CSerialDataFrame code ?

Because you are passing a implicitly shared object (i.e. QString) between two threads.

http://doc.trolltech.com/3.3/threads.html#9
http://doc.trolltech.com/3.3/shclass.html

Another question, what should I use instead of qDebug to keep a trace of what (should) going on ?

First you check whether you can use qDebug() or not, but you can always try writing messages to a text file.