Why do you make it yourself so difficult by using threads?
Did you know that you can have a perfectly responsive user interface without using threads?

Anyway, use signals and slots. You probably will need to rewrite your threading code if you followed the Qt documentation.
http://labs.trolltech.com/blogs/2006...-the-headache/
http://labs.trolltech.com/blogs/2010...oing-it-wrong/

If I may give you some advice: do not use threads for device IO operations like reading files or sending something over a socket UNLESS it is required if the device is blocking. Sockets are not blocking when you don't use the blocking functions.
Only use a thread if you want to decode or encode some data and even this can be made asynchronous.