well, i have tried an example and i can say for sure that u can use QFile in a subclass of QThread. Here is the code i used:

Qt Code:
  1. void MyThread::run()
  2. {
  3. bool doneReading;
  4.  
  5. file = new QFile("C:\\Documents and Settings\\am002bh\\Desktop\\practice.pro");
  6. if (!file->open(QIODevice::Append | QIODevice::Text))
  7. return;
  8.  
  9. QTextStream out(file);
  10. out << "The magic number is: " << 49 << "\n";
  11.  
  12. }
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issue must be somewhere else